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Part Number AD9984

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High Performance
10-bit Display Interface
Preliminary Technical Data
AD9984
Rev. PrB
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703
© 2005 Analog Devices, Inc. All rights reserved.
FEATURES
10-bit analog-to-digital converters
170 MSPS maximum conversion rate
Low PLL clock jitter at 170 MSPS
Automatic Gain Matching
Automated offset adjustment
2:1 input mux
Power-down via dedicated pin or serial register
4:4:4, 4:2:2, and DDR output format modes
Variable output drive strength
Odd/even field detection
External clock input
Regenerated Hsync output
Programmable output high impedance control
Hsyncs per Vsyncs counter
Pb-free package
APPLICATIONS
Advanced TVs
Plasma display panels
LCDTV
HDTV
RGB graphics processing
LCD monitors and projectors
Scan converters
FUNCTIONAL BLOCK DIAGRAM
2:1
MUX
10-bit ADC
Clamp
Auto Clamp
Level Adjust
Sync
Processing
PLL
Power Management
Voltage
Refs
Serial Register
Pr/Red
IN
1
10
Pr/Red
IN
0
Y/Green
IN
1
10
Y/Green
IN
0
Y/Green
OUT
Pb/Blue
IN
1
10
Pb/Blue
IN
0
Cb/Blue
OUT
10
10-bit ADC
PGA
Clamp
Auto Clamp
Level Adjust
10
10-bit ADC
PGA
Clamp
Auto Clamp
Level Adjust
10
Hsync 1
Hsync 0
Vsync 1
Vsync 0
SOGIN 1
SOGIN 0
2:1
MUX
2:1
MUX
2:1
MUX
2:1
MUX
2:1
MUX
SDA
SCL
REFHI
REFLO
EXTCLK/COAST
CLAMP
FILT
DATACK
SOGOUT
2:1
MUX
10-bit ADC
PGA
Clamp
Auto Offset
Sync
Processing
PLL
Power Management
Voltage
Refs
Serial Register
Pr/Red
IN
1
10
Pr/Red
IN
0
Y/Green
IN
1
10
Y/Green
IN
0
Y/Green
OUT
Pb/Blue
IN
1
10
Pb/Blue
IN
0
Cb/Blue
OUT
10
10-bit ADC
PGA
Clamp
Auto Offset
10
10-bit ADC
Clamp
Auto Offset
10
Hsync 1
Hsync 0
Vsync 1
Vsync 0
SOGIN 1
SOGIN 0
2:1
MUX
2:1
MUX
2:1
MUX
2:1
MUX
2:1
MUX
SDA
SCL
REFHI
REFLO
EXTCLK/COAST
CLAMP
FILT
DATACK
SOGOUT
HSOUT
Cb/Cr/Red
OUT
O/E Field
VSOUT/A0
Auto Gain
Auto Gain
Auto Gain
Ou
t
p
ut
Da
ta
F
o
r
ma
tt
e
r
Ou
t
p
ut
Da
ta
F
o
r
ma
tt
e
r
Figure 1.
GENERAL DESCRIPTION
The AD9984 is a complete 10-bit 170 MSPS monolithic analog
interface optimized for capturing YPbPr video and RGB
graphics signals. Its 170 MSPS encode rate capability and full-
power analog bandwidth of 300 MHz support all HDTV video
modes up to 1080p as well as graphics resolutions up to UXGA
(1600 x 1200 at 60 Hz).
The AD9984 includes a 170MHz triple ADC with an internal
reference, a PLL, and programmable gain, offset, and clamp
control. The user provides only a +1.8V power supply and an
analog input. Three-state CMOS outputs may be powered from
1.8V to 3.3V.
The AD9984's on-chip PLL generates a sample clock from the
tri-level sync (for YPbPr video) or the horizontal sync (for RGB
graphics). Sample clock output frequencies range from 10 to
170 MHz. With internal COAST generation, the PLL maintains
its output frequency in the absence of sync input. A 32-step
sampling clock phase adjustment is provided. Output data,
sync, and clock phase relationships are maintained.
The Auto Offset feature can be enabled to automatically restore
the signal reference levels and to automatically calibrate out any
offset differences between the three channels. The Auto
Channel-to-channel gain matching feature can be enabled to
minimize any gain mismatches between the three channels.
The AD9984 also offers full sync processing for composite sync
and sync-on-green applications. A clamp signal is generated
internally or may be provided by the user through the CLAMP
input pin.
Fabricated in an advanced CMOS process, the AD9984 is
provided in a space-saving 80-pin Pb- free LQFP surface mount
plastic package and is specified over the 0°C to +70°C
temperature range.
AD9984
Preliminary Technical Data
Rev. PrB | Page 2 of 45
TABLE OF CONTENTS
Analog Interface Specifications ...................................................... 2
Absolute Maximum Ratings............................................................ 4
Explanation of Test Levels ........................................................... 5
ESD Caution.................................................................................. 5
Pin Configuration and Function Descriptions............................. 6
Design Guide................................................................................... 11
General Description................................................................... 11
Digital Inputs .............................................................................. 11
Input Signal Handling................................................................ 11
Hsync and Vsync Inputs............................................................ 11
Serial Control Port ..................................................................... 11
Output Signal Handling............................................................. 11
Clamping ..................................................................................... 11
Gain and Offset Control............................................................ 12
Timing Diagrams........................................................................ 21
Hsync Timing ............................................................................. 22
Coast Timing............................................................................... 22
Output Formatter ....................................................................... 22
Two-Wire Serial Register Map...................................................... 24
Detailed 2-Wire Serial Control Register Descriptions .............. 30
Chip Identification ..................................................................... 30
PLL Divider Control .................................................................. 30
Clock Generator Control .......................................................... 30
Phase Adjust................................................................................ 31
Input Gain ................................................................................... 31
Input Offset ................................................................................. 31
Hsync Controls ........................................................................... 32
Vsync Controls ........................................................................... 32
Coast and Clamp Controls........................................................ 33
SOG Control ............................................................................... 35
Input and Power Control........................................................... 35
Output Control ........................................................................... 36
Two-Wire Serial Control Port....................................................... 41
Data Transfer via Serial Interface............................................. 41
PCB Layout Recommendations ............................................... 43
PLL ............................................................................................... 43
Outline Dimensions ....................................................................... 45
Ordering Guide .......................................................................... 45
REVISION HISTORY
11/05--Preliminary Version: Revision PrA
01/06--Preliminary Version: Revision PrB
Preliminary Technical Data
AD9984
Rev. PrB | Page 3 of 45
ANALOG INTERFACE SPECIFICATIONS
V
D
= 1.8 V, V
DD
= 3.3 V, PV
D
= 1.8 V, DAV
DD
= 1.8 V, ADC clock = maximum conversion rate , Full temperature range = 0°C to 70°C.
Table 1. Electrical Characteristics
Test
AD9984KSTZ-110
AD9984KSTZ-140
AD9984KSTZ-170
Parameter Temp
Level
Min
Typical Max
Min Typical Max Min
Typical Max
Units
RESOLUTION
Number of bits
LSB Size
10
0.098
10
0.098
10
0.098

Bits
% of Full Scale
DC ACCURACY
Differential
Nonlinearity
+25°C
Full
I
VI
+/-0.6
TBD
TBD
+/-0.8
TBD
TBD
+/-1.0
1
TBD
TBD

LSB
LSB
Integral
Nonlinearity
+25°C
Full
I
VI
+/-0.7
TBD
TBD
+/-1.0
TBD
TBD
+/-1.25
TBD
TBD
LSB
LSB
No Missing Codes
Full
VI
GNT
GNT
GNT
ANALOG INPUT
Input Voltage Range









Minimum
Full
VI
0.5
0.5 0.5
V
p­p
Maximum Full
VI
1.0
1.0
1.0
V
p­p
Gain
Tempco
+25°C
V
125
125 125
ppm/°C
Input Bias Current
+25°C
Full
IV
IV
1
1

1
1

1
1
A
A
Input Full-Scale Matching Full
VI
1
TBD
1
TBD
1
TBD % FS
Offset Adjustment Range Full
VI
50
50
50
% FS
SWITCHING PERFORMANCE
Maximum
Conversion
Rate
Full
VI
110
140

170


MSPS
Minimum
Conversion
Rate
Full IV
10
10
10
MSPS
Clock to Data Skew t
SKEW
Full IV -0.5 +2.0 -0.5
+2.0 -0.5
+2.0
ns
t
BUFF
Full
VI
4.7
4.7
4.7
uS
t
STAH
Full
VI
4.0
4.0
4.0
uS
t
DHO
Full
VI
0
0
0
uS
t
DAL
Full
VI
4.7
4.7
4.7
uS
t
DAH
Full
VI
4.0
4.0
4.0
uS
t
DSU
Full
VI
250
250
250
nS
t
STASU
Full
VI
4.7
4.7
4.7
uS
t
STOSU
Full
VI
4.0
4.0
4.0
uS
Maximum PLL Clock Rate Full
VI
110
140
170
MHz
Minimum PLL Clock Rate
Full
IV
10
10
10 MHz
Sampling Phase Tempco
Full
IV
15
15
15
pS/°C
DIGITAL INPUTS
2
Input Voltage, High (V
IH
) Full VI 1.0
1.0
1.0
V
Input Voltage, Low (V
IL
)
Full
VI
0.8 0.8 0.8
V
Input Current, High (I
IH
)
Full
V
-1.0 -1.0 -1.0
uA
Input Current, Low (I
IL
) Full
V
1.0 1.0 1.0
uA
Input Capacitance
+25
°C V
2
2 2
pF
DIGITAL OUTPUTS
Output Voltage, High
(V
OH
)
Full
VI
V
DD
-
0.1

V
DD
-
0.1

V
DD
-
0.1


V
Output Voltage, Low (V
OL
)
Full
VI
0.1 0.1 0.1
V
Duty Cycle, DATACK
Full
IV 45
50
55
45
50
55
45
50
55 %
Output Coding
Binary
Binary
Binary
POWER SUPPLY
V
D
Supply Voltage
Full
IV
1.7
1.8
1.9
1.7
1.8
1.9
1.755
1.8
1.9

V
V
DD
Supply Voltage
Full
IV 1.7
3.3
3.47
1.7
3.3
3.47 1.7
3.3
3.47 V
P
VD
Supply Voltage
Full
IV 1.7
1.8
1.9
1.7
1.8
1.9 1.7
1.8
1.9 V
DA
VDD
Supply Voltage
Full
IV 1.7
1.8
1.9
1.7
1.8
1.9 1.7
1.8
1.9 V
I
D
Supply Current (V
D
)
+25
°C V
mA
AD9984
Preliminary Technical Data
Rev. PrB | Page 4 of 45
Test
AD9984KSTZ-110
AD9984KSTZ-140
AD9984KSTZ-170
Parameter Temp
Level
Min
Typical
Max
Min Typical Max Min
Typical Max Units
I
DD
Supply Current (V
DD
)
1
+25
°C V
mA
IP
VD
Supply Current (P
VD
) +25
°C V
mA
IDA
VDD
Supply Current
(DA
VDD
)
+25
°C V
mA
Total Power Dissipation
Full
VI
mW
Power-Down Supply
Current
Full VI
mA
Power-Down
Dissipation Full VI
mW
DYNAMIC PERFORMANCE
Analog Bandwidth, Full
Power
+25°C
V 300
300 300
MHz
Crosstalk Full
V
60
60
60
dBc
THERMAL CHARACTERISTICS
0
JC
-Junction-to-Case
Thermal Resistance
V 16 16 16
°C/W
0
JA
-Junction-to-Ambient
Thermal Resistance
V
35
35
35
°C/W
1 Note about linearity at 170MSPS
Preliminary Technical Data
AD9984
Rev. PrB | Page 5 of 45
ABSOLUTE MAXIMUM RATINGS

Table 2.
Parameter Rating
V
D
1.98
V
V
DD
3.6
V
PV
D
1.98
V
DAV
DD
1.98
V
Analog Inputs
V
D
to 0.0 V
REFHI V
D
to 0.0 V
REFLO V
D
to 0.0 V
Digital Inputs
5 V to 0.0 V
Digital Output Current
20 mA
Operating Temperature
-25°C to + 85°C
Storage Temperature
-65°C to + 150°C
Maximum Junction Temperature
150°C
Maximum Case Temperature
150°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other conditions outside of those indicated in the operation
sections of this specification is not implied. Exposure to
absolute maximum ratings for extended periods may affect
device reliability.
EXPLANATION OF TEST LEVELS
Test Level
I.
100% production tested.
II.
100% production tested at 25°C and sample tested at
specified temperatures.
III.
Sample tested only.
IV.
Parameter is guaranteed by design and characterization
testing.
V.
Parameter is a typical value only.
VI.
100% production tested at 25°C; guaranteed by design and
characterization testing.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
AD9984
Preliminary Technical Data
Rev. PrB | Page 6 of 45
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
0
4
7
3
9
-
0
0
2
2
B
AIN0
3
GND
4
B
AIN1
7
GND
6
G
AIN0
5
V
D
(1.8V)
1
V
D
(1.8V)
8
SOGIN0
9
V
D
(1.8V)
10
G
AIN1
12
SOGIN1
13
V
D
(1.8V)
14
R
AIN0
15
GND
16
R
AIN1
17
PWRDN/TRI-ST
18
REFLO
19
NC
20
REFHI
11
GND
59
58
57
54
55
56
60
53
52
BLUE <4>
BLUE <5>
BLUE <6>
BLUE <9>
BLUE <8>
BLUE <7>
BLUE <3>
GND
V
DD
(3.3V)
51
GREEN <0>
49
GREEN <2>
48
GREEN <3>
47
GREEN <4>
46
GREEN <5>
45
GREEN <6>
44
GREEN <7>
43
GREEN <8>
42
GREEN <9>
41
DAV
DD
(1.8)
50
GREEN <1>
21
O
/
E
F
IE
L
D
22
VS
O
U
T
/A
0
23
H
S
O
U
T
24
S
OG
O
U
T
25
DA
TAC
K
26
V
DD
(3
. 3
V
)
27
G
ND
28
R
E
D
<9
>
29
R
E
D
<
8
>
30
R
E
D
<
7
>
31
R
E
D
<
6
>
32
R
E
D
<5
>
33
R
E
D
<
4
>
34
R
E
D
<
3
>
35
R
E
D
<
2
>
36
R
E
D
<
1
>
37
R
E
D
<
0
>
38
V
DD
(3
. 3
V
)
39
G
ND
40
G
ND
80
G
ND
79
P
V
D
(1
. 8
V
)
78
FI
LT
77
G
ND
76
P
V
D
( 1
. 8
V
)
75
G
ND
74
P
V
D
(1
. 8
V
)
73
C
LA
M
P
72
EX
T
C
L
K
/C
O
A
S
T
71
VS
Y
NC
0
70
H
SY
NC
0
69
VS
Y
NC
1
68
H
SY
NC
1
67
S
C
L
66
S
DA
65
G
ND
64
V
DD
(3
. 3
V
)
63
B
L
U
E
<
0
>
62
B
L
U
E
<
1
>
61
B
L
U
E
<
2
>
PIN 1
AD9984
TOP VIEW
(Not to Scale)
Figure 2. Top View (Pins Down)
Table 3. Complete Pinout List
Pin Type
Mnemonic
Function
Value
Pin No.
Inputs R
AIN0
Channel 0 Analog Input for Converter R
0.0 V to 1.0 V
14
R
AIN1
Channel 1 Analog Input for Converter R
0.0 V to 1.0 V
16
G
AIN0
Channel 0 Analog Input for Converter G
0.0 V to 1.0 V
6
G
AIN1
Channel 1 Analog Input for Converter G
0.0 V to 1.0 V
10
B
AIN0
Channel 0 Analog Input for Converter B
0.0 V to 1.0 V
2
B
AIN1
Channel 1 Analog Input for Converter B
0.0 V to 1.0 V
4
HSYNC0
Horizontal Sync Input for Channel 0
3.3 V CMOS
70
HSYNC1
Horizontal Sync Input for Channel 1
3.3 V CMOS
68
VSYNC0
Vertical Sync Input for Channel 0
3.3 V CMOS
71
VSYNC1
Vertical Sync Input for Channel 1
3.3 V CMOS
69
SOGIN0
Input for Sync-on-Green Channel 0
0.0 V to 1.0 V
8
SOGIN1
Input for Sync-on-Green Channel 1
0.0 V to 1.0 V
12
EXTCK
External Clock Input
3.3 V CMOS
72
1
CLAMP
External Clamp Input Signal
3.3 V CMOS
73
COAST
External PLL Coast Signal Input
3.3 V CMOS
72
1
PWRDN
Power-Down Control
3.3 V CMOS
17
Outputs RED
[9:0]
Outputs
of Converter R, Bit 9 is the MSB
3.3 V CMOS
28­37
GREEN [9:0]
Outputs of Converter G, Bit 9 is the MSB
3.3 V CMOS
42­51
BLUE [9:0]
Outputs of Converter B, Bit 9 is the MSB
3.3 V CMOS
54­63
DATACK
Data Output Clock
3.3 V CMOS
25
Preliminary Technical Data
AD9984
Rev. PrB | Page 7 of 45
Pin Type
Mnemonic
Function
Value
Pin No.
HSOUT
Hsync Output Clock (Phase-Aligned with DATACK)
3.3 V CMOS
23
VSOUT
Vsync Output Clock
3.3 V CMOS
22
2
SOGOUT
Sync-on-Green Slicer Output
3.3 V CMOS
24
O/E FIELD
Odd/Even Field Output
3.3V CMOS
21
References
FILT
Connection for External Filter Components for Internal PLL
78
REFLO
Connection for External Capacitor for Input Amplifier
18
REFHI
Connection for External Capacitor for Input Amplifier
20
Power Supply
V
D
Analog Power Supply
1.8 V
1, 5, 9, 13
V
DD
Output Power Supply
1.8 V or 3.3 V
26, 38, 52, 64
PV
D
PLL Power Supply
1.8 V
74, 76, 79
DAV
DD
Digital Logic Power Supply
1.8 V
41
GND
Ground
0
V
Control
SDA
Serial Port Data I/O
3.3 V CMOS
3
66
SCL
Serial Port Data Clock (100 kHz maximum)
3.3 V CMOS
3
67
A0
Serial Port Address Input
3.3 V CMOS
22
2
1
EXTCLK and COAST share the same pin.
2
VSOUT and A0 share the same pin.
3
SDA and SCL should be isolated with a FET. See I2C Bus Hardware Considerations in Two-Wire Serial Control Port section.
AD9984
Preliminary Technical Data
Rev. PrB | Page 8 of 45
Table 4.Pin Function Descriptions
Pin Description
INPUTS
RAIN0
Analog Input for the Red Channel 0.
GAIN0
Analog Input for the Green Channel 0.
BAIN0
Analog Input for the Blue Channel 0.
RAIN1
Analog Input for the Red Channel 1.
GAIN1
Analog Input for the Green Channel 1.
BAIN1
Analog Input for the Blue Channel 1.
High impedance inputs that accept the red, green, and blue channel graphics signals, respectively. The three
channels are identical and can be used for any colors, but colors are assigned for convenient reference. They
accommodate input signals ranging from 0.5 V to 1.0 V full scale. Signals should be ac-coupled to these pins to
support clamp operation.
HSYNC0
Horizontal Sync Input Channel 0.
HSYNC1
Horizontal Sync Input Channel 1.
These inputs receive a logic signal that establishes the horizontal timing reference and provides the frequency
reference for pixel clock generation. The logic sense of this pin can be automatically determined by the chip or
manually controlled by Serial Register 0x12, Bits [5:4] (Hsync polarity). Only the leading edge of Hsync is used by the
PLL; the trailing edge is used in clamp timing. When Hsync polarity = 0, the falling edge of Hsync is used. When Hsync
Polarity = 1 , the rising edge is active. The input includes a Schmitt trigger for noise immunity.
VSYNC0
Vertical Sync Input Channel 0.
VSYNC1
Vertical Sync Input Channel 1.
These are the inputs for vertical sync and provide timing information for generation of the field (odd/even) and
internal Coast generation. The logic sense of this pin can be automatically determined by the chip or manually
controlled by Serial Register 0x14, Bits [5:4] (Vsync polarity).
SOGIN0
Sync-on-Green Input Channel 0.
SOGIN1
Sync-on-Green Input Channel 1.
These inputs are provided to assist with processing signals with embedded sync, typically on the green channel. The
pin is connected to a high speed comparator with an internally generated threshold. The threshold level can be
programmed in 8 mV steps to any voltage between 8 mV and 256 mV above the negative peak of the input signal.
The default voltage threshold is 128 mV. When connected to an AC coupled graphics signal with embedded sync, it
produces a noninverting digital output on SOGOUT. This is usually a composite sync signal, containing both vertical
and horizontal sync information that must be separated before passing the horizontal sync signal for Hsync
processing. When not used, this input should be left unconnected. For more details on this function and how it
should be configured, refer to the Sync-on-Green section.
CLAMP
External Clamp Input (Optional).
This logic input may be used to define the time during which the input signal is clamped to ground or midscale. It
should be exercised when the reference DC level is known to be present on the analog input channels, typically
during the back porch of the graphics signal. The CLAMP pin is enabled by setting the control bit clamp function to 1,
(Register 0x18, Bit 4; default is 0). When disabled, this pin is ignored and the clamp timing is determined internally by
counting a delay and duration from the trailing edge of the Hsync input. The logic sense of this pin can be auto-
matically determined by the chip or controlled by clamp polarity Register 0x1B, Bits [7:6]. When not used, this pin may
be left unconnected (there is an internal pull-down resistor) and the clamp function programmed to 0.
EXTCLK/COAST
Coast Input to Clock Generator (Optional).
This input may be used to cause the pixel clock generator to stop synchronizing with Hsync and continue producing a
clock at its current frequency and phase. This is useful when processing signals from sources that fail to produce
Hsync pulses during the vertical interval. The coast signal is generally not required for PC-generated signals. The logic
sense of this pin can be determined automatically or controlled by Coast polarity (Register 0x18, Bits [7:6]). When not
used and EXTCLK not used, this pin may be grounded and Coast polarity programmed to 1. Input Coast polarity
defaults to1 at power-up. This pin is shared with the EXTCLK function, which does not affect coast functionality. For
more details on EXTCLK, see the description in this section.
EXTCLK/COAST
External Clock.
This allows the insertion of an external clock source rather than the internally generated, PLL locked clock. EXTCLK is
enabled by programming Register 0x03, Bit 2 to 1. This pin is shared with the Coast function, which does not affect
EXTCLK functionality. For more details on Coast, see the above description in this section.
PWRDN
Power-Down Control
This pin can be used along with Register 0x1E, Bit 3 for manual power-down control. If manual power-down control is
selected (Register 0x1E, Bit 4) and this pin is not used, it is recommended to set the pin polarity (Register 0x1E, Bit 2)
to active high and hardwire this pin to ground with a 10 k
resistor.
Preliminary Technical Data
AD9984
Rev. PrB | Page 9 of 45
Pin Description
REFLO
REFHI
Input Amplifier Reference.
REFLO and REFHI are connected together through a 10 F capacitor; These are used for stability in the input ADC
circuitry. See Figure 5.
FILT
External Filter Connection.
For proper operation, the pixel clock generator PLL requires an external filter. Connect the filter shown in Figure 6 to
this pin. For optimal performance, minimize noise and parasitics on this node. For more information, see the PCB
Layout Recommendations section.
OUTPUTS
HSOUT
Horizontal Sync Output.
A reconstructed and phase-aligned version of the Hsync input. Both the polarity and duration of this output can be
programmed via serial bus registers. By maintaining alignment with DATACK and Data, data timing with respect to
Hsync can always be determined.
VSOUT/A0
Vertical Sync Output.
Pin shared with A0, serial port address. This can be either a separated Vsync from a composite signal or a direct pass
through of the Vsync signal. The polarity of this output can be controlled via a serial bus bit. The placement and
duration in all modes can be set by the graphics transmitter or the duration can be set by Register 0x14 and Register
0x15. This pin is shared with the A0 function, which does not affect Vsync Output functionality. For more details on
A0, see the description in the Serial Control Port section.
SOGOUT
Sync-On-Green Slicer Output.
This pin outputs one of four possible signals (controlled by Register 0x1D, bits [1:0]): raw SOG, raw Hsync, regenerated
Hsync from the filter, or the filtered Hsync. See the sync processing block diagram (see Figure 8) to view how this pin
is connected. Other than slicing off SOG, the output from this pin gets no other additional processing on the AD9984.
Vsync separation is performed via the sync separator.
O/E FIELD
Odd/Even Field Bit for Interlaced Video. This output will identify whether the current field (in an interlaced signal) is
odd or even.
SERIAL PORT
SDA
Serial Port Data I/O.
SCL
Serial Port Data Clock.
VSOUT/A0
Serial Port Address Input 0.
Pin shared with VSOUT. This pin selects the LSB of the serial port device address, allowing two Analog Devices parts to
be on the same serial bus. A high impedance external pull-up resistor enables this pin to be read at power-up as 1, or
a high impedance, external pull-down resistor enables this pin to be read at power-up as a 0 and not interfere with
the VSOUT functionality. For more details on VSOUT, see the Outputs section in this table.
DATA OUTPUTS
RED [9:0]
Data Output, Red Channel.
GREEN [9:0]
Data Output, Green Channel.
BLUE [9:0]
Data Output, Blue Channel.
The main data outputs.
Bit 9 is the MSB. The delay from pixel sampling time to output is fixed. When the sampling time is changed by
adjusting the phase register, the output timing is shifted as well. The DATACK and HSOUT outputs are also moved, so
the timing relationship among the signals is maintained.
DATA CLOCK
OUTPUT
DATACK
Data Clock Output.
This is the main clock output signal used to strobe the output data and HSOUT into external logic. Four possible
output clocks can be selected with Register 0x20, Bits [7:6]. Three of these are related to the pixel clock (pixel clock,
90° phase-shifted pixel clock and 2× frequency pixel clock). They are produced either by the internal PLL clock
generator or EXTCLK and are synchronous with the pixel sampling clock. The fourth option for the data clock output
is an internally generated 1/2x pixel clock.
The sampling time of the internal pixel clock can be changed by adjusting the phase register (Register 0x04). When
this is changed, the pixel related DATACK timing is also shifted. The data, DATACK, and HSOUT outputs are all moved
so that the timing relationship among the signals is maintained.
AD9984
Preliminary Technical Data
Rev. PrB | Page 10 of 45
Pin Description
POWER SUPPLY
V
D
(1.8 V)
Main Power Supply.
These pins supply power to the main elements of the circuit. They should be as quiet and filtered as possible.
V
DD
(1.8 V­3.3 V)
Digital Output Power Supply.
A large number of output pins (up to 35) switching at high speed (up to 170 MHz) generates a lot of power supply
transients (noise). These supply pins are identified separately from the V
D
pins, so special care can be taken to
minimize output noise transferred into the sensitive analog circuitry. If the AD9984 is interfacing with lower voltage
logic, V
DD
may be connected to a lower supply voltage (as low as 1.8 V) for compatibility.
PV
D
(1.8 V)
Clock Generator Power Supply.
The most sensitive portion of the AD9984 is the clock generation circuitry. These pins provide power to the clock PLL
and help the user design for optimal performance. The designer should provide quiet, noise-free power to these pins.
DAV
DD
(1.8 V)
Digital Input Power Supply. This supplies power to the digital logic.
GND
Ground.
The ground return for all circuitry on-chip. It is recommended that the AD9984 be assembled on a single solid ground
plane, with careful attention to ground current paths.
Preliminary Technical Data
AD9984
Rev. PrB | Page 11 of 45
DESIGN GUIDE
GENERAL DESCRIPTION
The AD9984 is a fully integrated solution for capturing analog
RGB or YPbPr signals and digitizing them for display on
advanced TVs, flat panel monitors, projectors, and other types
of digital displays. Implemented in a high-performance CMOS
process, the interface can capture signals with pixel rates of up
to 170 MHz.
The AD9984 includes all necessary input buffering, signal DC
restoration (clamping), offset and gain (brightness and contrast)
adjustment, pixel clock generation, sampling phase control, and
output data formatting. All controls are programmable via a
two-wire serial interface (I
2
C
®
). Full integration of these
sensitive analog functions makes system design straightforward
and less sensitive to the physical and electrical environment.
With a typical power dissipation of less than 900 mW and an
operating temperature range of 0°C to 70°C, the device requires
no special environmental considerations.
DIGITAL INPUTS
All digital inputs on the AD9984 operate to 3.3 V CMOS levels.
The following digital inputs are 5 V tolerant (Applying 5 V to
them will not cause any damage.): Hsync0, Hsync1, Vsync0,
Vsync1, SOGIN0, SOGIN1, SDA, SCL and CLAMP.
INPUT SIGNAL HANDLING
The AD9984 has six high-impedance analog input pins for the
red, green, and blue channels. They accommodate signals
ranging from 0.5 V to 1.0 V p-p.
Signals are typically brought onto the interface board with a
DVI-I connector, a 15-pin D connector, or RCA connectors.
The AD9984 should be located as close as possible to the input
connector. Signals should be routed using matched-impedance
traces (normally 75 ) to the IC input pins.
At the input pins the signal should be resistively terminated
(75 to the signal ground return) and capacitively coupled to
the AD9984 inputs through 47 nF capacitors. These capacitors
form part of the DC restoration circuit.
In an ideal world of perfectly matched impedances, the best
performance can be obtained with the widest possible signal
bandwidth. The wide bandwidth inputs of the AD9984
(300 MHz) can track the input signal continuously as it moves
from one pixel level to the next and can digitize the pixel during
a long, flat pixel time. In many systems, however, there are
mismatches, reflections, and noise, which can result in excessive
ringing and distortion of the input waveform. This makes it
more difficult to establish a sampling phase that provides good
image quality. It has been shown that a small inductor in series
with the input is effective in rolling off the input bandwidth
slightly and providing a high quality signal over a wider range
of conditions. Using a Fair-Rite #2508051217Z0-High Speed,
Signal Chip Bead Inductor in the circuit shown in Figure 3 gives
good results in most applications.
RGB
INPUT
R
AIN
G
AIN
B
AIN
47nF
75
04739-003
Figure 3. Analog Input Interface Circuit
HSYNC AND VSYNC INPUTS
The interface also accepts Hsync and Vsync signals, which are
used to generate the pixel clock, clamp timing, Coast and field
information. These can be either a sync signal directly from the
graphics source, or a preprocessed TTL or CMOS level signal.
The Hsync input includes a Schmitt trigger buffer for immunity
to noise and signals with long rise times. In typical PC-based
graphic systems, the sync signals are simply TTL-level drivers
feeding unshielded wires in the monitor cable. As such, no
termination is required.
SERIAL CONTROL PORT
The serial control port is designed for 3.3 V logic; however, it is
tolerant of 5 V logic signals. Refer to the section of I2C Bus
Hardware Considerations in the Two-Wire Serial Control Port
description.
OUTPUT SIGNAL HANDLING
The digital outputs are designed to operate from 1.8 V to
3.3 V (V
DD
).
CLAMPING
RGB Clamping
To properly digitize the incoming signal, the DC offset of the
input must be adjusted to fit the range of the on-board ADCs.
Most graphics systems produce RGB signals with black at
ground and white at approximately 0.75 V. However, if sync
signals are embedded in the graphics, the sync tip is often at
ground and black is at 300 mV. Then white is at approximately
1.0 V. Some common RGB line amplifier boxes use emitter-
follower buffers to split signals and increase drive capability.
This introduces a 700 mV dc offset to the signal, which must be
removed for proper capture by the AD9984.
The key to clamping is to identify a portion (time) of the signal
when the graphic system is known to be producing black. An
offset is then introduced that results in the ADC producing a
black output (Code 0x00) when the known black input is
present. The offset then remains in place when other signal
levels are processed, and the entire signal is shifted to eliminate
offset errors.
AD9984
Preliminary Technical Data
Rev. PrB | Page 12 of 45
In most PC graphics systems, black is transmitted between
active video lines. With CRT displays, when the electron beam
has completed writing a horizontal line on the screen (at the
right side), the beam is deflected quickly to the left side of the
screen (called horizontal retrace) and a black signal is provided
to prevent the beam from disturbing the image.
In systems with embedded sync, a blacker-than-black signal
(Hsync) is produced briefly to signal the CRT that it is time to
begin a retrace. Because the input is not at black level at this
time, it is important to avoid clamping during Hsync. Fortu-
nately, there is virtually always a period following Hsync, called
the `back porch', where a good black reference is provided. This
is the time when clamping should be done.
The clamp timing can be established by simply exercising the
CLAMP pin at the appropriate time with clamp source
(Register 0x18, Bit 4) = 1. The polarity of this signal is set by
the clamp polarity bit (Register 0x1B, Bits [7:6]).
A simpler method of clamp timing employs the AD9984
internal clamp timing generator. The clamp placement register
(Register 0x19) is programmed with the number of pixel
periods that should pass after the trailing edge of Hsync
before clamping starts. A second register, clamp duration,
(Register 0x1A) sets the duration of the clamp. These are both
8-bit values, providing considerable flexibility in clamp
generation. The clamp timing is referenced to the trailing edge
of Hsync because, though Hsync duration can vary widely, the
back porch (black reference) always follows Hsync. A good
starting point for establishing clamping is to set the clamp
placement to 0x04 (providing 4 pixel periods for the graphics
signal to stabilize after sync) and set the clamp duration to
0x28 (giving the clamp 40 pixel periods to reestablish the
black reference).
Clamping is accomplished by placing an appropriate charge on
the external input coupling capacitor. The value of this
capacitor affects the performance of the clamp. If it is too small,
there will be a significant amplitude change during a horizontal
line time (between clamping intervals). If the capacitor is too
large, then it will take excessively long for the clamp to recover
from a large change in incoming signal offset. The
recommended value (47 nF) results in recovering from a step
error of 100 mV to within 1 LSB in 30 lines with a clamp
duration of 20 pixel periods on a 85 Hz XGA signal.
YPbPr Clamping
YPbPr graphic signals are slightly different from RGB signals in
that the dc reference level (black level in RGB signals) of color
difference signals is at the midpoint of the video signal rather
than at the bottom. The three inputs are composed of
luminance (Y) and color difference (Pb and Pr) signals. For
color differ-ence signals it is necessary to clamp to the midscale
range of the ADC range (512) rather than to the bottom of the
ADC range (0), while the Y channel is clamped to ground.
Clamping to midscale rather than ground can be accomplished
by setting the clamp select bits in the serial bus register. Each of
the three converters has its own selection bit so that they can be
clamped to either midscale or ground independently. These bits
are located in Register 0x18, Bits [3:1]. The midscale reference
voltage is internally generated for each converter.
GAIN AND OFFSET CONTROL
The AD9984 contains three programmable gain amplifiers
(PGAs), one for each of the three analog inputs. The range of
the PGA is sufficient to accommodate input signals with inputs
ranging from 0.5 V to 1.0 V full scale. The gain is set in three
9-bit registers (red gain [0x05, 0x06], green gain [0x07, 0x08],
blue gain [0x09, 0x0A]). For each of these registers, a gain
setting of 0 d corresponds to the highest gain, while a gain
setting of 511 d corresponds to the lowest gain. Note that
increasing the gain setting results in an image with less contrast.
The offset control shifts the analog input, resulting in a change
in brightness. Three 11-bit registers (red offset [0x0B, 0x0C],
green offset [0x0D, 0x0E], blue offset [0x0F, 0x10]) provide
independent settings for each channel. Note that the function of
the offset register depends on whether auto-offset is enabled
(Register 0x1B, Bit 5).
If manual offset is used, nine bits of the offset registers (for
the red channel Register 0x0B, Bits[6:0] plus Register 0x0C,
Bits [7:6]) control the absolute offset added to the channel. The
offset control provides ±255 LSBs of adjustment range, with one
LSB of offset corresponding to one LSB of output code.
Automatic Offset
In addition to the manual offset adjustment mode, the AD9984
also includes circuitry to automatically calibrate the offset for
each channel. By monitoring the output of each ADC during
the back porch of the input signals, the AD9984 can self-adjust
to eliminate any offset errors in its own ADC channels and any
offset errors present on the incoming graphics or video signals.
To activate the auto-offset mode, set Register 0x1B, Bit 5 to 1.
Next, the target code registers (0x0B through 0x10) must be
programmed. The values programmed into the target code
registers should be the output code desired from the AD9984
during the back porch reference time. For example, for RGB
signals, all three registers would normally be programmed to
Code 1, while for YPbPr signals the green (Y) channel is nor-
mally programmed to Code 1 and the blue and red channels
(Pb and Pr) are normally set to 512. The target code registers
have 11 bits per channel and are in twos complement format.
This allows any value between ­1024 and +1023 to be program-
med. Although any value in this range can be programmed, the
AD9984's offset range may not be able to reach every value.
Intended target code values range from (but are not limited to)
Preliminary Technical Data
AD9984
Rev. PrB | Page 13 of 45
­160 to ­1 and 1 to 160 when ground clamping, and 350 to 670
when midscale clamping. Note that a target code of 0 isn't valid.
Negative target codes are included in order to duplicate a fea-
ture that is present with manual offset adjustment. The benefit
that is being mimicked is the ability to easily adjust brightness
on a display. By setting the target code to a value that does not
correspond to the ideal ADC range, the end result is an image
that is either brighter or darker. A target code higher than ideal
results in a brighter image, while a target code lower than ideal
results in a darker image.
The ability to program a target code gives a large degree of
freedom and flexibility. While in most cases all channels are set
to either 1 or 512, the flexibility to select other values allows the
possibility of inserting intentional skews between channels. It
also allows the ADC range to be skewed so that voltages outside
of the normal range can be digitized. For example, setting the
target code to 40 allows the sync tip, which is normally below
black level, to be digitized and evaluated.
The internal logic for the auto-offset circuit requires 16 data
clock cycles to perform its function. This operation is executed
immediately after the clamping pulse. Therefore, it is important
to end the clamping pulse signal at least 16 data clock cycles
before active video. This is true whether using the AD9984's
internal clamp circuit or an external clamp signal. The auto-
offset function can be programmed to run continuously or on a
one-time basis (see auto-offset hold, Register 0x2C, Bit 4). In
continuous mode, the update frequency can be programmed
(Register 0x1B, Bits [4:3]). Continuous operation with updates
every 64 Hsyncs is recommended.
A guideline for basic auto-offset operation is shown in Table 5
and Table 6.
Table 5. RGB Auto-Offset Register Settings
Register Value
Comments
0x0B
0x00
Sets red target to 4
0x0C
0x80
Must be written
0x0D
0x00
Sets green target to 4
0x0E
0x80
Must be written
0x0F
0x00
Sets blue target to 4
0x10
0x80
Must be written
0x18, Bits [3:1]
000
Sets red, green, and blue
channels to ground clamp
0x1B, Bit [5:3]
110
Selects update rate and
enables auto-offset.
Table 6. PbPr Auto-Offset Register Settings
Register Value
Comments
0x0B
0x40
Sets Pr (red) target to 512
0x0C
0x00
Must be written
0x0D
0x00
Sets Y (green) target to 4
0x0E
0x80
Must be written
0x0F
0x40
Sets Pb (blue) target to 512
0x10
0x00
Must be written
0x18 Bits [3:1]
101
Sets Pb, Pr to midscale clamp
and Y to ground clamp
0x1B, Bit [5:3]
110
Selects update rate and
enables auto-offset
Automatic Gain Matching
The AD9984 includes circuitry to match the gains between the
three channels to within 1% of each other. Matching the gains of
each channel is necessary in order to achieve good color
balance on a display. On products without this feature, gain
matching is achieved by writing software which evaluates the
output of each channel, calculates gain mismatches, then writes
values to the gain registers of each channel to compensate. With
the Auto Gain Matching function, this software routine is no
longer needed.
To activate Auto Gain Matching, set register 3Ch, bit 2 to 1.
Auto Gain Matching has similar timing requirements to Auto
Offset. It requires 16 data clock cycles to perform its function,
starting immediately after the end of the clamp pulse. Unlike
Auto Offset it does not require that these 16 clock cycles occur
during the back porch reference time, although that is what is
recommended. During Auto Gain Matching operation, the data
outputs of the AD9984 are frozen (held at the value they had
just prior to operation). The Auto Gain Matching function can
be programmed to run continuously or on a one-time basis (see
Auto Gain Matching Hold, register 2Ch, bit 3). In continuous
mode, the update frequency can be programmed (register 1Bh,
bits 4:3). Continuous operation with updates every 64 Hsyncs is
recommended.
Sync-on-Green
The sync-on-green input operates in two steps. First, it sets a
baseline clamp level off of the incoming video signal with a
negative peak detector. Second, it sets the sync trigger level to
a programmable (Register 0x1D, Bits [7:3]) level (typically
128 mV) above the negative peak. The sync-on-green input
must be ac-coupled to the green analog input through its own
capacitor. The value of the capacitor must be 1 nF ±20%. If
sync-on-green is not used, this connection is not required. The
sync-on-green signal always has negative polarity.
R
AIN
B
AIN
G
AIN
SOG
47nF
47nF
47nF
1nF
04739-004
Figure 4. Typical Input Configuration
Reference Bypassing
REFLO and REFHI are connected to each other by a 10 F
capacitor. These references are used by the input ADC
circuitry.
AD9984
Preliminary Technical Data
Rev. PrB | Page 14 of 45
REFHI
REFLO
10
F
0
4
7
3
9
-
0
1
4
Figure 5. Input Amplifier Reference Capacitors
Clock Generation
A PLL is used to generate the pixel clock. The Hsync input pro-
vides a reference frequency to the PLL. A voltage controlled
oscillator (VCO) generates a much higher pixel clock frequency.
The pixel clock is divided by the PLL divide value (Register
0x01 and Register 0x02) and phase-compared with the Hsync
input. Any error is used to shift the VCO frequency and
maintain lock between the two signals.
The stability of this clock is a very important element in
providing the clearest and most stable image. During each pixel
time, there is a period during which the signal is slewing from
the old pixel amplitude and settling at its new value. Then there
is a time when the input voltage is stable, before the signal must
slew to a new value (see Figure 6). The ratio of the slewing time
to the stable time is a function of the bandwidth of the graphics
DAC and the bandwidth of the transmission system (cable and
termination). It is also a function of the overall pixel rate.
Clearly, if the dynamic characteristics of the system remain
fixed, then the slewing and settling time is likewise fixed. This
time must be subtracted from the total pixel period, leaving the
stable period. At higher pixel frequencies, the total cycle time is
shorter and the stable pixel time also becomes shorter.
PIXEL CLOCK
INVALID SAMPLE TIMES
04739-005
Figure 6. Pixel Sampling Times
Any jitter in the clock reduces the precision with which the
sampling time can be determined and must also be subtracted
from the stable pixel time. Considerable care has been taken in
the design of the AD9984's clock generation circuit to minimize
jitter. The clock jitter of the AD9984 is low in all operating
modes, making the reduction in the valid sampling time due to
jitter negligible.
The PLL characteristics are determined by the loop filter design,
the PLL charge pump current, and the VCO range setting. The
loop filter design is illustrated in Figure 7. Recommended
settings of the VCO range and charge pump current for VESA
standard display modes are listed in Table 9.
C
P
8nF
C
Z
80nF
R
Z
1.5k
FILT
PV
D
04739-006
Figure 7. PLL Loop Filter Detail
Four programmable registers are provided to optimize the
performance of the PLL. These registers are
1.
The 12-Bit Divisor Register. The input Hsync frequencies
can accommodate any Hsync as long as the product of the
Hsync and the PLL divisor falls within the operating range
of the VCO. The PLL multiplies the frequency of the Hsync
signal, producing pixel clock frequencies in the range of
10 MHz to 170 MHz. The divisor register controls the
exact multiplication factor. This register may be set to any
value between 2 and 4095 as long as the output frequency
is within range.
2.
The 2-Bit VCO Range Register. To improve the noise
performance of the AD9984, the VCO operating frequency
range is divided into four overlapping regions. The VCO
range register sets this operating range. The frequency
ranges for the four regions are shown in Table 7.
Table 7. VCO Frequency Ranges
PV1 PV0
Pixel Clock
Range (MHz)
KVCO
Gain (MHz/V)
0 0 10­21
150
0 1 21­42
150
1 0 42­84
150
1 1 84-170
150
3.
The 3-Bit Charge Pump Current Register. This register
varies the current that drives the low pass loop filter. The
possible current values are listed in Table 8.
Table 8. Charge Pump Current/Control Bits
Ip2 Ip1 Ip0 Current
(A)
0 0 0 50
0 0 1 100
0 1 0 150
0 1 1 250
1 0 0 350
1 0 1 500
1 1 0 750
1 1 1 1500
4.
The 5-Bit Phase Adjust Register. The phase of the gen-
erated sampling clock may be shifted to locate an optimum
Preliminary Technical Data
AD9984
Rev. PrB | Page 15 of 45
sampling point within a clock cycle. The phase adjust
register provides 32 phase-shift steps of 11.25° each. The
Hsync signal with an identical phase shift is available
through the HSOUT pin. Phase adjust is still available if an
external pixel clock is used. The COAST pin or the internal
coast is used to allow the PLL to continue to run at the
same frequency in the absence of the incoming Hsync
signal or during disturbances in Hsync (such as from
equalization pulses). This may be used during the vertical
sync period or at any other time that the Hsync signal is
unavailable. The polarity of the coast signal may be set
through the coast polarity register (Register 0x18,
Bits [6:5]). Also, the polarity of the Hsync signal may
be set through the Hsync polarity register (Register 0x12,
Bits [5:4]). For both Hsync and coast, a value of 1 is active
high. The internal coast function is driven off the Vsync
signal, which is typically a time when Hsync signals may be
disrupted with extra equalization pulses.
AD9984
Preliminary Technical Data
Rev. PrB | Page 16 of 45
Table 9. Recommended VCO Range and Charge Pump and Current Settings for Standard Display Formats
Standard
Resolution
Refresh Rate
(Hz)
Horizontal Frequency
(kHz)
Pixel Rate
(MHz)
PLL
Divider
VCORNGE
Current
VGA
640 × 480
60
31.500
25.175
800
00
101
72
37.700
31.500
832
01
011
75
37.500
31.500 840 01 011
85
43.300
36.000
832
01
100
SVGA
800 × 600
56
35.100
36.000
1024
01
100
60
37.900
40.000
1056
01
100
72
48.100
50.000
1040
01
100
75
46.900
49.500
1056
01
100
85
53.700
56.250
1048
01
101
XGA
1024 × 768
60
48.400
65.000
1344
10
100
70
56.500
75.000
1328
10
011
75
60.000
78.750
1312
10
100
80
64.000
85.500
1336
10
100
85
68.300
94.500
1376
10
011
SXGA
1280 × 1024
60
64.000
108.000
1688
10
100
75
80.000
135.000 1688
11 100
85
91.100
157.500 1728
11 100
UXGA
1600 × 1200
60
75.000
162.000
2160
11
100
TV 480i
30
15.750
13.510
858
00
010
480p 60
31.470
27.000 858 00 101
576i 30
15.625
13.500 864 00 010
576p 60
31.250
27.000 864 00 101
720p 60
45.000
74.250 1650
10 011
1035i
30
33.750
74.250 2200
10 011
1080i
60
33.750
74.250 2200
10 011
1080p
60
67.500
148.500 2200
11 100
Preliminary Technical Data
AD9984
Rev. PrB | Page 17 of 45
AD9984
SYNC
PROCESSOR
PLL CLOCK
GENERATOR
MUX
HSYNC FILTER
0
1
SOG OUT
OUT
OUT
HSYNC
COAST
DATACK
SOGIN0
1
COAST
0
4
7
4
0
-
0
-
0
1
2
CHANNEL
SELECT
SELECT
0
VSYNC1
HSYNC/VSYNC
COUNTER
Reg 26H, 27H
ODD/EVEN
FIELD
AD
1
AD
1
MUX
MUX
MUX
RH
3
FH
4
MUX
SP
5
SP
5
SP
5
MUX
4
5
3
2
1
ACTIVITY DETECT
POLARITY DETECT
REGENERATED HSYNC
FILTERED HSYNC
SET POLARITY
SP
5
VSYNC FILTER
and
AD
1
PD
2
AD
1
PD
2
AD
1
PD
2
AD
1
PD
2
MUX
SYNC
SLICER
SYNC
SLICER
VSYNC
HSYNC
HSYNC
HSYNC
HSYNC
VSYNC
SOGIN
and
REGENERATOR
Figure 8. Sync Processing Block Diagram
Sync Processing
The inputs of the sync processing section of the AD9984 are
combinations of digital Hsyncs and Vsyncs, analog sync-on-
green, or sync-on-Y signals, and an optional external coast
signal. From these signals it generates a precise, jitter-free clock
from its PLL; an odd-/even-field signal; Hsync and Vsync out
signals; a count of Hsyncs per Vsync; and a programmable SOG
output. The main sync processing blocks are the sync slicer,
sync separator, Hsync filter, Hsync regenerator, Vsync filter, and
Coast generator.
The sync slicer extracts the sync signal from the green graphics
or luminance video signal that is connected to the SOGIN input
and outputs a digital composite sync. The sync separator's task
is to extract Vsync from the composite sync signal, which can
come from either the sync slicer or the Hsync input. The Hsync
filter is used to eliminate any extraneous pulses from the Hsync
or SOGIN inputs, outputting a clean, low-jitter signal that is
appropriate for mode detection and clock generation. The
Hsync regenerator is used to recreate a clean, although not low
jitter, Hsync signal that can be used for mode detection and
counting Hsyncs per Vsync. The Vsync filter is used to elimi-
nate spurious Vsyncs, maintain a stable timing relationship
between the Vsync and Hsync output signals, and generate the
odd/even field output. The coast generator creates a robust
coast signal that allows the PLL to maintain its frequency in the
absence of Hsync pulses.
Sync Slicer
The purpose of the sync slicer is to extract the sync signal from
the green graphics or luminance video signal that is connected
to the SOGIN input. The sync signal is extracted in a two step
process. First, the SOG input is clamped to its negative peak,
(typically 0.3 V below the black level). Next, the signal goes to a
comparator with a variable trigger level (set by Register 0x1D,
Bits [7:3]), but nominally 0.128 V above the clamped level. The
sync slicer output is a digital composite sync signal containing
both Hsync and Vsync information (see Figure 9).
AD9984
Preliminary Technical Data
Rev. PrB | Page 18 of 45
04739-015
SOG INPUT
SOGOUT OUTPUT
CONNECTED TO
HSYNCIN
NEGATIVE PULSE WIDTH = 40 SAMPLE CLOCKS
COMPOSITE
SYNC
AT HSYNCIN
VSYNCOUT
FROM SYNC
SEPARATOR
­300mV
­300mV
700mV MAXIMUM
0mV
Figure 9. Sync Slicer and Sync Separator Output
Sync Separator
As part of sync processing, the sync separator's task is to extract
Vsync from the composite sync signal. It works on the idea that
the Vsync signal stays active for a much longer time than the
Hsync signal. By using a digital low-pass filter and a digital
comparator, it rejects pulses with small durations (such as
Hsyncs and equalization pulses) and only passes pulses with
large durations, such as Vsync (see Figure 9).
The threshold of the digital comparator is programmable for
maximum flexibility. To program the threshold duration, write
a value (N) to Register 0x11. The resulting pulse width is N ×
200 nS. So, if N = 5 the digital comparator threshold is 1 S.
Any pulse less than 1 S is rejected, while any pulse greater than
1 S passes through.
There are two things to keep in mind when using the sync
separator. First, the resulting clean Vsync output is delayed
from the original Vsync by a duration equal to the digital
comparator threshold (N × 200 nS). Second, there is some
variability to the 200 nS multiplier value. The maximum
variability over all operating conditions is ±20% (160 nS to 240
nS). Since normal Vsync and Hsync pulse widths differ by a
factor of about 500 or more, the 20% variability is not an issue.
Hsync Filter and Regenerator
The Hsync filter is used to eliminate any extraneous pulses from
the Hsync or SOGIN inputs, outputting a clean, low-jitter signal
that is appropriate for mode detection and clock generation.
The Hsync regenerator is used to recreate a clean, although not
low jitter, Hsync signal that can be used for mode detection and
counting Hsyncs per Vsync. The Hsync regenerator has a high
degree of tolerance to extraneous and missing pulses on the
Hsync input, but is not appropriate for use by the PLL in
creating the pixel clock due to jitter.
The Hsync regenerator runs automatically and requires no
setup to operate. The Hsync filter requires the setting up of a
filter window. The filter window sets a periodic window of time
around the regenerated Hsync leading edge where valid Hsyncs
are allowed to occur. The general idea is that extraneous pulses
on the sync input occur outside of this filter window and thus
are filtered out. In order to set the filter window timing, pro-
gram a value (x) into Register 0x23. The resulting filter window
time is ±x times 25 nS around the regenerated Hsync leading
edge. Just as for the sync separator threshold multiplier, allow a
±20% variance in the 25 nS multiplier to account for all oper-
ating conditions (20 nS to 30 nS range).
A second output from the Hsync filter is a status bit (0x25,
Bit 1) that tells whether extraneous pulses were present on the
incoming sync signal or not. Many times extraneous pulses are
included for copy protection purposes, so this status bit can be
used to detect that.
The filtered Hsync (rather than the raw Hsync/SOGIN signal)
for pixel clock generation by the PLL is controlled by
Register 0x20, Bit 2. The regenerated Hsync (rather than
the raw Hsync/ SOGIN signal) for the sync processing is
controlled by Register 0x20, Bit 1. Use of the filtered Hsync
and regenerated Hsync is recommended. See Figure 10 for an
illustration of a filtered Hsync.
Preliminary Technical Data
AD9984
Rev. PrB | Page 19 of 45
HSYNCOUT
VSYNC
FILTER
WINDOW
EXPECTED
EDGE
FILTER
WINDOW
EQUALIZATION
PULSES
HSYNCIN
04739-016
Figure 10. Sync Processing Filter
Vsync Filter and Odd/Even Fields
The Vsync filter is used to eliminate spurious Vsyncs, maintain
a stable timing relationship between the Vsync and Hsync
output signals, and generate the odd/even field output.
The filter works by examining the placement of Vsync with
respect to Hsync and if necessary shifting it in time slightly.
The goal is to keep the Vsync and Hsync leading edges from
switching at the same time, thus eliminating confusion as to
when the first line of a frame occurs. Register 0x14, Bit 2
enables the Vsync filter. Use of the Vsync filter is recommended
for all cases, including interlaced video, and is required when
using the Hsyncs per Vsync counter. Figure 12 illustrates
even/odd field determination in two situations.
FIELD 1
FIELD 0
SYNC SEPARATOR THRESHOLD
FIELD 1
FIELD 0
2
3
2
1
4
4
3
1
HSYNCIN
VSYNCIN
VSYNCOUT
O/E FIELD
ODD FIELD
QUADRANT
04739-017
Figure 11.
AD9984
Preliminary Technical Data
Rev. PrB | Page 20 of 45
FIELD 1
FIELD 0
SYNC SEPARATOR THRESHOLD
FIELD 1
FIELD 0
2
3
2
1
4
4
3
1
HSYNCIN
VSYNCIN
VSYNCOUT
O/E FIELD
EVEN FIELD
QUADRANT
04739-018
Figure 12. Vsync Filter--Odd/Even
Power Management
To meet display requirements for low standby power, the
AD9984 includes a power-down mode. The power-down state
can be controlled manually (via Pin 17 or Register 0x1E, Bit 3),
or completely automatically by the chip. If automatic control is
selected (0x1E, Bit 4), the AD9984's decision is based on the
status of the sync detect bits (Register 0x24, Bits 2, 3, 6, and 7).
If either an Hsync or a sync-on-green input is detected on any
input, the chip powers up, or else it powers down. For manual
control, the AD9984 allows flexibility of control through both a
dedicated pin and a register bit. The dedicated pin allows a
hardware watchdog circuit to control power-down, while the
register bit allows power-down to be controlled by software.
With manual power-down control, the polarity of the power-
down pin must be set (0x1E, Bit 2) whether the pin is used or
not. If unused, it is recommended to set the polarity to active
high and hardwire the pin to ground with a 10 k resistor.
In power-down mode, there are several circuits that continue to
operate as normal. The serial register and sync detect circuits
maintain power so that the AD9984 can be woken up from
its power-down state. The bandgap circuit maintains power
because it is needed for sync detection. The sync-on-green and
SOGOUT functions continue to operate because the SOGOUT
output is needed when sync detection is performed by a
secondary chip. All of these circuits require minimal power to
operate. Typical standby power on the AD9984 is about 50 mW.
There are two options that can be selected when in power-
down. These are controlled by Bits 0 and 1 in Register 0x1E.
The first bit controls whether the SOGOUT pin is in high impe-
dance or not. In most cases, the user will not place SOGOUT in
high impedance during normal operation. The option to put
SOGOUT in high impedance is included mainly to allow for
factory testing modes. The second option keeps the AD9984
powered up while placing only the outputs in high impedance.
This option is useful when the data outputs from two chips are
connected on a PCB and the user wants to switch
instantaneously between the two.
Table 10.Power-Down Control and Mode Descriptions
Inputs
Mode
Auto Power-Down
Control
1
Power-Down
2
Sync
Detect
3
Powered-On or Comments
Power-Up 1
X
1
Everything
Power-Down 1
X
0
Only the serial bus, sync activity detect,
SOG, bandgap reference
Power-Up 0
0
X
Everything
Power-Down 0
1
X
Only the serial bus, sync activity detect,
SOG, bandgap reference
1
Auto power-down control is set by Register 0x1E, Bit 4.
2
Power-down is controlled by OR'ing Pin 17 with Register 0x1E, Bit 3. The polarity of Pin 17 is set by Register 0x1E, Bit 2.
3
Sync detect is determined by OR'ing Register 0x24, Bits 2, 3, 6, and 7.
Preliminary Technical Data
AD9984
Rev. PrB | Page 21 of 45
TIMING DIAGRAMS
The following timing diagrams show the operation of the
AD9984.The output data clock signal is created so that its rising
edge always occurs between data transitions and can be used to
latch the output data externally. There is a pipeline in the
AD9984, which must be flushed before valid data becomes
available. This means six data sets are presented before valid
data is available.
t
PER
t
DCYCLE
t
SKEW
DATACK
DATA
HSOUT
04739-007
Figure 13. Output Timing
DATAIN
P0
P1
P2
P5
P3
P4
P9
P6
P8
P10
P11
P7
HSIN
DATACLK
8 CLOCK CYCLE DELAY
DATAOUT
P0
P1
P2
P3
2 CLOCK CYCLE DELAY
HSOUT
04739-008
Figure 14. 4:4:4 Timing Mode
DATAIN
P0
P1
P2
P5
P3
P4
P9
P6
P8
P10
P11
P7
HSIN
DATACLK
8 CLOCK CYCLE DELAY
CB/CROUT
B0
R0
B2
R2
YOUT
Y0
Y1
Y2
Y3
2 CLOCK CYCLE DELAY
1. PIXEL AFTER HSOUT CORRESONDS TO BLUE INPUT.
2. EVEN NUMBER OF PIXEL DELAY BETWEEN HSOUT AND DATAOUT.
HSOUT
0
4
7
3
9
-
0
0
9
Figure 15. 4:2:2 Timing Mode
AD9984
Preliminary Technical Data
Rev. PrB | Page 22 of 45
DATAIN
P0
P1
P2
P5
P3
P4
P9
P6
P8
P10
P11
P7
HSIN
DATACLK
8 CLOCK CYCLE DELAY
2 CLOCK CYCLE DELAY
DDR NOTES
1. OUTPUT DATACLK MAY BE DELAYED 1/4 CLOCK PERIOD IN THE REGISTERS.
2. SEE PROJECT DOCUMENT FOR VALUES OF F (FALLING EDGE) AND R (RISING EDGE).
3. FOR DDR 4:2:2 MODE: TIMING IS IDENTICAL, VALUES OF F AND R CHANGE.
GENERAL NOTES
1. DATA DELAY MAY VARY ± ONE CLOCK CYCLE, DEPENDING ON PHASE SETTING.
2. ADCs SAMPLE INPUT ON FALLING EDGE OF DATACLK.
3. HSYNC SHOWN IS ACTIVE HIGH (EDGE SHOWN IS LEADING EDGE).
HSOUT
04739-010
F0 R0 F1 R1 F2 R2 F3 R3
Figure 16. DDR Timing Mode
HSYNC TIMING
The Hsync is processed in the AD9984 to eliminate ambiguity
in the timing of the leading edge with respect to the phase-
delayed pixel clock and data.
The Hsync input is used as a reference to generate the pixel
sampling clock. The sampling phase can be adjusted with
respect to Hsync through a full 360° in 32 steps via the phase
adjust register (to optimize the pixel sampling time). Display
systems use Hsync to align memory and display write cycles, so
it is important to have a stable timing relationship between
Hsync output (HSOUT) and the data clock (DATACK).
Three things happen to Hsync in the AD9984. First, the polarity
of Hsync input is determined and thus has a known output
polarity. The known output polarity can be programmed either
active high or active low (Register 0x12, Bit 3). Second, HSOUT
is aligned with DATACK and data outputs. Third, the duration
of HSOUT (in pixel clocks) is set via Register 0x13. HSOUT is
the sync signal that should be used to drive the rest of the
display system.
COAST TIMING
In most computer systems, the Hsync signal is provided
continuously on a dedicated wire. In these systems, the coast
input and function are unnecessary and should not be used.
In some systems, however, Hsync is disturbed during the
vertical sync period (Vsync). In some cases, Hsync pulses
disappear. In other systems, such as those that employ
composite sync (Csync) signals or embedded sync-on-green,
Hsync may include equalization pulses or other distortions
during Vsync. To avoid upsetting the clock generator during
Vsync, it is important to ignore these distortions. If the pixel
clock PLL sees extraneous pulses, it attempts to lock to this new
frequency, and will have changed frequency by the end of the
Vsync period. It then takes a few lines of correct Hsync timing
to recover at the beginning of a new frame, resulting in a tearing
of the image at the top of the display.
The coast input is provided to eliminate this problem. It is an
asynchronous input that disables the PLL input and holds the
clock at its current frequency. The PLL can free run for several
lines without significant frequency drift. Coast can be generated
internally by the AD9984 (see Register 0x18) or can be provided
externally by the graphics controller.
When internal Coast is selected (Register 0x18, Bit 7 = 0, and
Register 0x14, Bits [7:6] to select source), Vsync is used as a
basis for determining the position of Coast. The internal coast
signal is enabled a programmed number of Hsync periods
before the periodic Vsync signal (Precoast Register 0x16) and
dropped a programmed number of Hsync periods after Vsync
(Postcoast Register 0x17). It is recommended that the Vsync
filter be enabled when using the internal Coast function to
allow the AD9984 to determine precisely the number of
Hsyncs/Vsync and their location. In many applications where
disruptions occur and coast is used, values of 2 for Precoast
and 10 DDR for Postcoast are sufficient to avoid most
extraneous pulses.
OUTPUT FORMATTER
The output formatter is capable of generating several output
formats to be presented to the 30 data output pins. The output
formats and the pin assignments for each format are listed in
Table 11. Also, there are several clock options for the output
clock. The user may select the pixel clock, a 90° phase-shifted
pixel clock, a 2× pixel clock, or a fixed frequency 40 MHz clock
for test purposes. The output clock may also be inverted.
Data output is available as 30 pin RGB or YCbCr or if either
4:2:2 or 4:4:4 DDR is selected, a secondary channel is available.
This secondary channel is always 4:2:2 DDR and allows the
flexibility of having a second channel with the same video data
that can be utilized by either another display or even a storage
device. Depending on the choice of output modes, the primary
output can be 30 pins, 20 pins or as little as 15 pins.
Preliminary Technical Data
AD9984
Rev. PrB | Page 23 of 45
Mode Descriptions
·
4:4:4--All channels come out with their 10 data bits at the
same time. Data is aligned to the negative edge of the clock
for easy capture. This is the normal 30 bit output mode for
RGB or 4:4:4 YCbCr.
·
4:2:2--Red and green channels contain 4:2:2 formatted
data (20 pins) with Y data on the green channel and Cb, Cr
data on the red channel. Data is aligned to the negative
edge of the clock. The blue channel contains the secondary
channel with Cb, Y, Cr, Y formatted 4:2:2 DDR data. The
data edges are aligned to both edges of the pixel clock, so
use of the 90° clock may be necessary to capture the DDR
data.
·
4:4:4 DDR--This mode puts out full 4:4:4 data on 15 bits of
the red and green channels, thus saving 15 pins. The first
half (RGB [14:0]) of the 30-bit data is sent on the rising
edge and the second half (RGB [29:15]) is sent on the
falling edge. DDR 4:2:2 data is sent on the blue channel, as
in 4:2:2 mode.
RGB [29:0] = R [9:0] + G [9:0] + B [9:0], so RGB [29:15] =
R [9:0] + G [9:5] and RGB [14:0] = G [4:0] + B [9:0]


Table 11. Output Formats
Port Red
Green
Blue
Bit
9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
4:4:4 Red/Cr
Green/Y
Blue/Cb
4:2:2
Cb, Cr
Y
DDR 4:2:2
Cb,Cr Y,Y
DDR
G [4:0]
DDR
B [9:0]
N/A
DDR 4:2:2
Cb,Cr
4:4:4
DDR
DDR
R [9:0]
DDR
G [9:5]
N/A
DDR 4:2:2
Y,Y
AD9984
Preliminary Technical Data
Rev. PrB | Page 24 of 45
TWO-WIRE SERIAL REGISTER MAP
The AD9984 is initialized and controlled by a set of registers, which determine the operating modes. An external controller is employed
to write and read the control registers through the two-wire serial interface port.
Table 12.Control Register Map
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name
Description
0x00 RO 7:0
Chip Revision
An 8-bit register that represents the silicon revision level.
0x01 R/W
7:0
0110 1001
PLL Div MSB
This register is for bits [11:4] of the PLL divider. Larger values
mean the PLL operates at a faster rate. This register should be
loaded first whenever a change is needed. (This will give the PLL
more time to lock).
1
0x02 R/W
7:4
1101 ****
PLL Div LSB
Bits [7:4] LSBs of the PLL Divider Word. Links to the PLL Div MSB
to make a 12-bit register.
1
0x03 R/W
7:6
01** ****
VCO/CPMP
Bits [7:6] VCO Range. Selects VCO frequency range.
(See PLL description).
5:3
**00 1***
Bits [5:3] Charge Pump Current. Varies the current that drives the
low-pass filter. (See PLL description).
2
**** *0**
Bit 2. External Clock Enable
0x04 R/W
7:3
1000 0***
Phase Adjust
ADC Clock Phase Adjustment. Larger values mean more delay.
(1 LSB = T/32).
0x05 R/W
6:0 *100
0000
Red Gain
MSBs
7-Bit Red Channel Gain Control. Controls ADC input range
(contrast) of each respective channel. Bigger values give less
contrast.
0x06 R/W
7:0 00**
****
Red Gain
LSBs
Linked with Register 0x05 to form the 9-bit red gain that controls
the ADC input range (contrast) of the red channel. A lower value
corresponds to a higher gain.
1
0x07 R/W
6:0 *100
0000
Green Gain
MSBs
7-Bit Green Channel Gain Control. Controls ADC input range
(contrast) of each respective channel. Bigger values give less
contrast.
0x08 R/W
7:0 00**
****
Green Gain
LSBs
Linked to Register 0x07 to form the 9-bit green gain that controls
the ADC input range (contrast) of the green channel. A lower
value corresponds to a higher gain.
1
0x09 R/W
6:0 *100
0000
Blue Gain
MSBs
7-Bit Blue Channel Gain Control. Controls ADC input range
(contrast) of each respective channel. Bigger values give less
contrast.
0x0A R/W
7:0 00**
****
Blue Gain
LSBs
Linked to Register 0x09 to form the 9-bit blue gain that controls
the ADC input range (contrast) of the blue channel. A lower value
corresponds to a higher gain.
1
0x0B R/W
7:0 0100
0000
Red Offset
MSBs
8-Bit MSBs of the Red Channel Offset Control. Controls dc offset
(brightness) of each respective channel. Bigger values decrease
brightness.
1
0x0C R/W
7 000*
****
Red Offset
LSBs
Linked to Register 0x0B to form the 11-bit red offset that controls
the dc offset (brightness) of the red channel in auto-offset mode.
0x0D R/W
7:0 0100
0000
Green Offset
MSBs
8-Bit MSBs of the Green Channel Offset Control. Controls dc
offset (brightness) of each respective channel. Bigger values
decrease brightness.
1
0x0E R/W
7 000*
****
Green Offset
LSBs
Linked to Register 0x0D to form the 11-bit green offset that
controls the dc offset (brightness) of the green channel in auto-
offset mode.
Preliminary Technical Data
AD9984
Rev. PrB | Page 25 of 45
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name Description
0x0F R/W 7:0 0100
0000
Blue Offset
MSBs
8-Bit MSBs of the Red Channel Offset Control. Controls dc offset
(brightness) of each respective channel. Bigger values decrease
brightness.
1
0x10 R/W 7 000*
****
Blue Offset
LSBs
Linked to Register 0x0F to form the 11-bit blue offset which
controls the dc offset (brightness) of the blue channel in auto-
offset mode.
0x11 R/W 7:0
0010 0000
Sync
Separator
Threshold
This register sets the threshold of the sync separator's digital
comparator.
0x12 R/W 7
0*** ****
Hsync
Control
Active Hsync Override.
0 = The chip determines the active Hsync source.
1 = The active Hsync Source is set by 0x12, Bit 6.
6
*0** ****
Selects the source of the Hsync for PLL and sync processing. This
bit is used only if 0x12, Bit 7 is set to 1 or if both syncs are active.
0 = Hsync is from Hsync input pin.
1 = Hsync is from SOG.
5
**0* ****
Hsync Polarity Override.
0 = The chip selects the Hsync input polarity.
1 = The polarity of the input Hsync is controlled by 0x12, Bit 4.
This applies to both Hsync0 and Hsync1.
4
***1 ****
Hsync input polarity: this bit is used only if 0x12, Bit 5 is set to 1.
0 = Active low input Hsync.
1 = Active high input Hsync.
3
**** 1***
Sets the polarity of the Hsync output signal.
0 = Active low Hsync output.
1 = Active high Hsync output.
0x13 R/W 7:0
0010 0000
Hsync
Duration
Sets the number of pixel clocks that Hsync out is active.
0x14 R/W 7
0*** ****
Vsync Control
Active Vsync Override.
0 = The chip determines the active Vsync source.
1 = The active Vsync source is set by 0x14, Bit 6.
6
*0** ****
Selects the source of Vsync for the sync processing. This bit is
used only if 0x14, Bit 7 is set to 1.
0 = Vsync is from the Vsync input pin
1 = Vsync is from the sync separator.
5
**0* ****
Vsync Polarity Override.
0 = The chip selects the input Vsync polarity.
1 = The polarity of the input Vsync is set by 0x14, Bit 4.
This applies to both Vsync0 and Vsync1.
4
***1 ****
Vsync input polarity: this bit is used only if 0x14, Bit 5 is set to 1.
0 = Active low input Vsync.
1 = Active high input Vsync.
3
**** 1***
Sets the polarity of the output Vsync signal.
0 = Active low output Vsync.
1 = Active high output Vsync.
2
**** *0**
0 = The Vsync filter is disabled.
1 = The Vsync filter is enabled.
This needs to be enabled when using the Hsync to Vsync counter.
1
**** **0*
Enables the Vsync duration block. This is designed to be used
with the Vsync filter.
0 = Vsync output duration is unchanged.
1 = Vsync output duration is set by Register 0x15.
0x15 R/W 7:0
0000 1010
Vsync
Duration
Sets the number of Hsyncs that Vsync out is active. This is only
used if 0x14, Bit 1 is set to 1.
0x16 R/W 7:0
0000 0000
Precoast
The number of Hsync periods to coast prior to Vsync.
0x17 R/W 7:0
0000 0000
Postcoast
The number of Hsync periods to coast after Vsync.
AD9984
Preliminary Technical Data
Rev. PrB | Page 26 of 45
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name Description
0x18 R/W 7
0*** ****
Coast and
Clamp
Control
Coast Source.
Selects the source of the coast signal.
0 = Using internal coast generated from Vsync..
1 = Using external coast signal from external Coast pin.
6
*0** ****
Coast Polarity Override.
0 = The chip selects the external Coast polarity.
1 = The polarity of the external Coast signal is set by 0x18, Bit 5.
5
**1* ****
Coast Input Polarity.
This bit is used only if 0x18, Bit 6 is set to 1.
0 = Active low external coast.
1 = Active high external coast.
4
***0 ****
Clamp Source Select.
0 = Use the internal clamp generated from Hsync.
1 = Use the external clamp signal.
3
**** 0***
Red
Clamp.
0 = Clamp the red channel to ground.
1 = Clamp the red channel to midscale.
2
**** *0**
Green
Clamp.
0 = Clamp the green channel to ground.
1 = Clamp the green channel to midscale.
1
**** **0*
Blue
Clamp.
0 = Clamp the blue channel to ground.
1 = Clamp the blue channel to midscale.
0
**** ***0
Must be set to 0 for proper operation.
0x19 R/W 7:0
0000 1000
Clamp
Placement
Places the clamp signal an integer of clock periods after the
trailing edge of the Hsync signal.
0x1A R/W 7:0
0010 0000
Clamp
Duration
Number of clock periods that the clamp signal is actively
clamping.
0x1B R/W 7
0*** ****
Clamp and
Offset
External clamp polarity override.
0 = The chip selects the clamp polarity.
1 = The polarity of the clamp signal is set by 0x1B, Bit 6.
6
*1** ****
External Clamp Input Polarity. This bit is used only if 0x1B, Bit 7 is
set to 1 .
0 = Active low external clamp.
1 = Active high external clamp.
5
**0* ****
0 = Auto-offset is disabled.
1 = Auto-offset is enabled (offsets become the desired clamp
code).
4:3
***1 1***
This selects how often the auto-offset circuit operates. 00 = every
3 clamps; 01 = 48 clamps; 10 = every 192 clamps; 11 = every 3
Vsyncs.
2:0
**** *011
Must be written to default (011) for proper operation.
0x1C R/W 7:0
1111 1111
TestReg0
Must be set to 0xFF for proper operation.
0x1D R/W 7:3
0111 1***
SOG Control
SOG slicer threshold. Sets the voltage level of the SOG slicer's
comparator.
2
**** *0**
SOGOUT
Polarity.
Sets the polarity of the signal on the SOGout pin.
0 = Active low SOGout.
1 = Active high SOGout.
1:0
**** **00
SOGOUT
Select.
00 = Raw SOG from sync slicer (Sog0 or Sog1).
01 = Raw Hsync (Hsync0 or Hsync1).
10 = Regenerated sync from sync filter.
11 = Filtered sync from sync filter.
0x1E R/W 7
*** ****
Power
Channel Select Override.
0 = The chip determines which input channels to use.
1 = The input channel selection is determined by 0x1E, Bit 6.
Preliminary Technical Data
AD9984
Rev. PrB | Page 27 of 45
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name Description
6
*0** ****
Channel
Select.
Input channel select: this is used only if 0x1E, Bit 7 is set to 1, or if
syncs are present on both channels.
0 = Channel 0 syncs and data are selected.
1 = Channel 1 syncs and data are selected.
5
**1* ****
Programmable
Bandwidth.
0 = Low analog input bandwidth.
1 = High analog input bandwidth.
4
***1 ****
Power-Down Control Select.
0 = Manual power-down control.
1 = Auto power-down control.
3
**** 0***
Power-Down.
0 = Normal operation.
1 = Power-down.
2
**** *0**
Power-Down Pin Polarity.
0 = Active low.
1 = Active high.
1
**** **0*
Power-Down Fast Switching Control.
0 = Normal power-down operation.
1 = The chip stays powered up and the outputs are put in high
impedance mode.
0
**** ***0
SOGOUT High Impedance Control.
0 = SOGOUT operates as normal during power-down.
1 = SOGOUT is in high impedance during power-down.
0x1F R/W 7:5
100* ****
Output Select
1
Output Mode.
100 = 4:4:4 output mode.
101 = 4:2:2 output mode.
110 = 4:4:4--DDR output mode.
4
***1 ****
Primary
Output
Enable.
0 = Primary output is in high impedance state.
1 = Primary output is enabled.
3
**** 0***
Secondary Output Enable.
0 = Secondary output is in high impedance state.
1 = Secondary output is enabled.
2:1
**** *10*
Output Drive Strength.
00 = Low output drive strength.
01 = Medium output drive strength.
10 = High output drive strength.
11 = High output drive strength.
Applies to all outputs except VSOUT.
0
**** ***0
Output Clock Invert.
0 = Noninverted Pixel Clock.
1 = Inverted Pixel Clock.
Applies to all clocks output on DATACK.
0x20 R/W 7:6
0*** ****
Output Select
2
Output Clock Select.
00 = Pixel clock.
01 = 90° phase shifted pixel clock.
10 = 2× pixel clock.
11 = 0.5x pixel clock.
5
*0** ****
Output
High
Impedance.
0 = Normal outputs.
1 = All outputs except SOGOUT in high impedance mode.
4
**0* ****
SOG High Impedance.
0 = Normal SOG output
1 = SOGOUT pin is in high impedance mode.
3
***0 ****
Field Output Polarity.
Sets the polarity of the field output signal.
0 = Active low => even field, active high => odd field.
1 = Active low => odd field, active high => even field.
AD9984
Preliminary Technical Data
Rev. PrB | Page 28 of 45
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name Description
2
**** 1***
PLL Sync Filter Enable.
0 = PLL uses raw Hsync/SOG.
1 = PLL uses filtered Hsync/SOG.
1
**** *0**
Sync Processing Input Select.
Selects the sync source for the sync processor.
0 = Sync processing uses raw Hsync/SOGIN.
1 = Sync processing uses regenerated Hsync from sync filter.
0
Must be set to 1 for proper operation.
0x21 R/W 7:0
0010 0000
Must be set to default for proper operation.
0x22 R/W 7:0
0011 0010
Must be set to default for proper operation.
0x23 R/W 7:0
0000 1010
Sync Filter
Window
Width
Sets the window of time around the regenerated Hsync leading
edge (in 25 nS steps) that sync pulses are allowed to pass
through.
0x24
RO
7
_*** ****
Sync Detect
Hsync0 Detection Bit.
0 = Hsync0 is not active.
1 = Hsync0 is active.
6
*_** ****
Hsync1 Detection Bit.
0 = Hsync 1 is not active.
1 = Hsync 1 is active.
5
**_* ****
Vsync 0 Detection Bit.
0 = Vsync0 is not active.
1 = Vsync0 is active.
4
***_ ****
Vsync1 Detection Bit.
0 = Vsync1 is not active.
1 = Vsync1 is active.
3
**** _***
SOG0 Detection Bit
0 = SOG0 is not active.
1 = SOG0 is active.
2
**** *_**
SOG1 Detection Bit
0 = SOG1 is not active.
1 = SOG1 is active.
1
**** **_*
Coast Detection Bit.
0 = External Coast is not active.
1 = External Coast is active.
0
****
***_
Clamp Detection Bit.
0 = External clamp is not active.
1 = External clamp is active.
0x25
RO
7
_*** ****
Sync Polarity
Detect
Hsync 0 Polarity.
0 = Hsync0 polarity is active low.
1 = Hsync0 polarity is active high.
6
*_** ****
Hsync1 Polarity.
0 = Hsync1 polarity is active low.
1 = Hsync1 polarity is active high.
5
**_* ****
Vsync0 Polarity.
0 = Vsync0 polarity is active low.
1 = Vsync0 polarity is active high.
4 ***_
****
Vsync1 Polarity.
0 = Vsync1 polarity is active low.
1 = Vsync1 polarity is active high.
3
**** _***
Coast Polarity.
0 = External COAST polarity is active low.
1 = External COAST polarity is active high.
2
**** *_**
Clamp Polarity.
0 = External clamp polarity is active low.
1 = External clamp polarity is active high.
1 ****
**_*
Extraneous Pulses Detected.
0 = No equalization pulses detected on Hsync.
1 = Extraneous pulses detected on Hsync.
0x26 RO
7:0
Hsyncs Per
Vsync MSBs
MSBs of Hsyncs per Vsync count.
Preliminary Technical Data
AD9984
Rev. PrB | Page 29 of 45
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name Description
0x27 RO
7:4
Hsyncs
Per
Vsync LSBs
LSBs of Hsyncs per Vsync count.
0x28
R/W
7:0
1011 1111
TestReg1
Must be written to 0xBF for proper operation.
0x29
R/W
7:0
0000 0010
TestReg2
Must be written to 0x02 for proper operation.
0x2A RO
7:0
TestReg3
Read only bits for future use.
0x2B RO
7:0
TestReg4
Read only bits for future use.
0x2C
R/W
7:5
000* ****
Offset Hold
Must be written to default for proper operation.
4 ***0
****
Auto-Offset
Hold.
Disables the auto-offset and holds the feedback result.
0 = One time update.
1 = Continuous update.
3:0 ****
0000
Must be written to default for proper operation.
0x2D
R/W
7:0
1111 0000
TestReg5
Must be written to 0xE8 for proper operation.
0x2E
R/W
7:0
1111 0000
TestReg6
Must be written to 0xE0 for proper operation.
0x3C
R/W
7:4
0000 ****
Auto Gain
Must be set to default for proper operation
3
****
0***
Auto Gain Matching Hold
0 = Disables Auto Gain updates and holds the current Auto Offset
values.
1 = Allows Auto Gain to update continuously
2:0
****
*000
Auto Gain Matching Enable
000 = Auto Gain is disabled
110= Auto Gain is enabled
1
Functions with more than eight control bits, such as PLL divide ratio, gain, and offset, are only updated when the LSBs are written to (for example, Register 0x02 for
PLL divide ratio).
AD9984
Preliminary Technical Data
Rev. PrB | Page 30 of 45
DETAILED 2-WIRE SERIAL CONTROL REGISTER DESCRIPTIONS
CHIP IDENTIFICATION
0x00 7:0 Chip
Revision
An 8-bit register that represents the silicon revision
.
PLL DIVIDER CONTROL
0x01
7:0
PLL Divide Ratio MSBs
The eight MSBs of the 12-bit PLL divide ratio
PLLDIV.
The PLL derives a pixel clock from the incoming
Hsync signal. The pixel clock frequency is then
divided by an integer value, such that the output is
phase-locked to Hsync. This PLLDIV value
determines the number of pixel times (pixels plus
horizontal blanking overhead) per line. This is
typically 20% to 30% more than the number of active
pixels in the display.
The 12-bit value of the PLL divider supports divide
ratios from 2 to 4095 as long as the output frequency
is within range. The higher the value loaded in this
register, the higher the resulting clock frequency with
respect to a fixed Hsync frequency.
VESA has established some standard timing specifi-
cations, which will assist in determining the value for
PLLDIV as a function of horizontal and vertical
display resolution and frame rate (see Table 9).
However, many computer systems do not conform
precisely to the recommendations and these numbers
should be used only as a guide. The display system
manufacturer should provide automatic or manual
means for optimizing PLLDIV. An incorrectly set
PLLDIV usually produces one or more vertical noise
bars on the display. The greater the error, the greater
the number of bars produced.
The power-up default value of PLLDIV is 1693.
PLLDIVM = 0x69, PLLDIVL = 0xDX.
The AD9984 updates the full divide ratio only when
the LSBs are written. Writing to this register by itself
does not trigger an update.
0x02
7:4
PLL Divide Ratio LSBs
The four LSBs of the 12-bit PLL divide ratio PLLDIV.
The power-up default value of PLLDIV is 1693.
PLLDIVM = 0x69, PLLDIVL = 0xDX.
CLOCK GENERATOR CONTROL
0x03
7:6
VCO Range Select
Two bits that establish the operating range of the clock
generator. VCORNGE must be set to correspond to
the desired operating frequency (incoming pixel rate).
The PLL gives the best jitter performance at high
frequencies. For this reason, in order to output low
pixel rates and still get good jitter performance, the
PLL actually operates at a higher frequency but then
divides down the clock rate afterwards. See Table 13
for the pixel rates for each VCO range setting. The
PLL output divisor is automatically selected with the
VCO range setting. The power-up default value is 01.
Table 13. VCO Ranges
VCO Range
Pixel Rates
00 10-21
01 21-42
10 42-84
11 84-95
0x03 5:3 Charge
Pump
Current
Three bits that establish the current driving the loop
filter in the clock generator. The current must be set to
correspond with the desired operating frequency. The
power-up default value is current = 001.
Table 14. Charge Pump Currents
Ip2 Ip1 Ip0 Current
0 0 0 50
0 0 1 100
0 1 0 150
0 1 1 250
1 0 0 350
1 0 1 500
1 1 0 750
1 1 1 1500
0x03 2
External
Clock
Enable
This bit determines the source of the pixel clock.
Table 15. External Clock Select Settings
EXTCLK Function
0
Internally generated clock
1
Externally provided clock signal
A Logic 0 enables the internal PLL that generates the
pixel clock from an externally provided Hsync.
A Logic 1 enables the external EXTCLK input pin. In
this mode, the PLL Divide Ratio (PLLDIV) is ignored.
The clock phase adjust (Phase) is still functional. The
power-up default value is EXTCLK = 0.
Preliminary Technical Data
AD9984
Rev. PrB | Page 31 of 45
PHASE ADJUST
0x04 7:3
Phase adjustment for the DLL to generate the ADC
clock. A 5 bit value that adjusts the sampling phase in
32 steps across one pixel time. Each step represents an
11.25° shift in sampling phase. The power up default
is 16.
INPUT GAIN
0x05
6:0
Red Channel Gain Adjust MSBs
The 7-Bit Red Channel Gain Control. The AD9984
can accommodate input signals with a full-scale range
of between 0.5 V and 1.0 V p-p. Setting the red gain to
511 corresponds to an input range of 1.0 V. A red gain
of 0 establishes an input range of 0.5 V. Note that
increasing red gain results in the picture having less
contrast (the input signal uses fewer of the available
converter codes). Values written to this register will
not be updated until the LSB register (R0x06) has also
been written. The power-up default is 1000000.
0x06 7:6 Red Channel Gain Adjust LSBs
The 2 Bit LSBs of the Red Channel Gain Control.
Along with the 7 MSBs of gain control in the previous
register, there are 9 bits of gain control. Default power
up value is 00.
0x07 6:0 Green Channel Gain Adjust MSBs
The 7-Bit Green Channel Gain Control. See red
channel gain adjust above. Register update requires
writing 0x00 to Register 0x08.
0x08 7:6 Green Channel Gain Adjust LSBs
The 2-Bit LSBs of the Green Channel Gain Control.
Along with the 7 MSBs of gain control in the previous
register, there are 9 bits of gain control. Default power-
up value is 00.
0x09
6:0
Blue Channel Gain Adjust MSBs
The 7-Bit Blue Channel Gain Control. See red channel
gain adjust above. Register update requires writing
0x00 to Register 0x0A.
0x0A
7:6
Blue Channel Gain Adjust LSBs
The 2-Bit LSBs of the Blue Channel Gain Control.
Along with the 7 MSBs of gain control in the previous
register, there are 9 bits of gain control. Default power-
up value is 00.
INPUT OFFSET
0x0B
7:0
Red Channel Offset MSBs
The 8-Bit MSB of the Red Channel Offset Control.
Along with the 1 LSBs in the following register, there
are 11 bits of dc offset control in the red channel. The
offset control shifts the analog input, resulting in a
change in brightness. Note that the function of the
offset register depends on whether auto-offset is
enabled (Register 0x1B, Bit 5).
If auto-offset is disabled, the 9 bits of the offset reg-
isters (Bits [6:0] of the offset MSB register plus
Bits [7:6] of the following register) control the absolute
offset added to the channel (for the red channel,
Register 0x0B, Bits[6:0] plus Register 0x0C,
Bits [7:6])control the absolute offset added to the
channel. The offset control provides a ±255 LSBs of
adjustment range, with 1 LSB of offset corresponding
to 1 LSB of output code.
If auto-offset is enabled, the 11-bit offset (comprised
of the 8 bits of the MSB register and Bits [7:5] of the
following register) determines the clamp target code.
The 11-bit offset consists of 1 sign bit plus 10 bits. If
the register is programmed to 530 DDR, then the
output code is equal to 530 DDR at the end of the
clamp period. Note that incrementing the offset
register setting by 1 LSB adds 1 LSB of offset,
regardless of the auto-offset setting. Values written to
this register are not updated until the LSB register
(Register 0x0C) has also been written.
0x0C
7:5
Red Channel Offset LSBs
The LSBs of the red channel offset control combine
with the 8 bits of MSB in the previous register to make
11 bits of offset control.
0x0D
7:0
Green Channel Offset MSBs
The 8-Bit Green Channel Offset Control. See red
channel offset (0x0B). Update of this register occurs
only when Register 0x0E is also written.
0x0E
7:5
Green Channel Offset LSBs
The LSBs of the green channel offset control combine
with the 8 bits of MSB in the previous register to make
11 bits of offset control.
0x0F
7:0
Blue Channel Offset MSBs
The 8-Bit Blue Channel Offset Control. See red
channel offset (0x0B). Update of this register occurs
only when Register 0x10 is also written.
AD9984
Preliminary Technical Data
Rev. PrB | Page 32 of 45
0x10
7:5
Blue Channel Offset LSBs
The LSBs of the blue channel offset control combine
with the 8 bits of MSB in the previous register to make
11 bits of offset control.
HSYNC CONTROLS
0x11
7:0
Sync Separator Threshold
This register sets the threshold of the sync separator's
digital comparator. The value written to this register is
multiplied by 200 nS to get the threshold value.
Therefore, if a value of 5 is written, the digital
comparator threshold is 1 S and any pulses less than
1 S are rejected by the sync separator. There is some
variability to the 200 nS multiplier value. The
maximum variability over all operating conditions is
±20% (160 nS to 240 nS). Since normal Vsync and
Hsync pulse widths differ by a factor of about 500 or
more, the 20% variability is not an issue. The power-
up default value is 32 DDR.
0x12
7
Hsync Source Override
This is the active Hsync override. Setting this to 0
allows the chip to determine the active Hsync source.
Setting it to 1 uses Bit 6 of Register 0x12 to determine
the active Hsync source. Power-up default value is 0.
Table 16.Active Hsync Source Override
Override Result
0
Hsync Source determined by chip
1
Hsync Source determined by user
Register 0x12, Bit 6
0x12 6
Hsync
Source
This bit selects the source of the Hsync for PLL and
sync processing--only if Bit 7 of Register 0x12 is set to
1 or if both syncs are active. Setting this bit to 0
specifies the Hsync from the input pin. Setting it to 1
selects Hsync from SOG. Power-up default is 0.
Table 17. Active Hsync Select Settings
Select Result
0 Hsync
Input
1
Hsync from SOG
0x12
5
Hsync Input Polarity Override
This bit determines whether the chip selects the Hsync
input polarity or if it is specified. Setting this bit to 0
allows the chip to automatically select the polarity of
the input Hsync; setting it to 1 indicates that Bit 4 of
Register 0x12 specifies the polarity. Power-up default
is 0.
Table 18. Hsync Input Polarity Override Settings
Override Bit
Result
0
Hsync Polarity Determined by Chip
1
Hsync Polarity Determined by User
Register 0x12, Bit 4
0x12
4
Input Hsync Polarity
If Bit 5 of Register 0x12 is 1, the value of this bit
specifies the polarity of the input Hsync. Setting this
bit to 0 indicates an active low Hsync; setting this bit
to 1 indicates an active high Hsync. Power-up default
is 1.
Table 19. Hsync Input Polarity Settings
Hsync Polarity Bit
Result
0
Hsync Input Polarity is Negative
1
Hsync Input Polarity is Positive
0x12 3
Hsync
Output
Polarity
This bit sets the polarity of the Hsync output. Setting
this bit to 0 sets the Hsync output to active low. Setting
this bit to 1 sets the Hsync output to active high.
Power-up default setting is 1.
Table 20. Hsync Output Polarity Settings
Hsync Output
Polarity Bit
Result
0
Hsync Output Polarity is Negative
1
Hsync Output Polarity is Positive
0x13 7:0 Hsync
Duration
An 8 bit register that sets the duration of the Hsync
output pulse. The leading edge of the Hsync output is
triggered by the internally-generated, phase-adjusted
PLL feedback clock. The AD9984 then counts a
number of pixel clocks equal to the value in this
register. This triggers the trailing edge of the Hsync
output, which is also phase-adjusted.
VSYNC CONTROLS
0x14 7
Vsync
Source
Override
This is the active Vsync override. Setting this to 0
allows the chip to determine the active Vsync source,
setting it to 1 uses Bit 6 of Register 0x14 to determine
the active Vsync source. Power-up default value is 0.
Table 21. Active Vsync Source Override
Override Result
0
Vsync source determined by chip
1
Vsync source determined by user
Register 0x14, Bit 6
Preliminary Technical Data
AD9984
Rev. PrB | Page 33 of 45
0x14 6
Vsync
Source
This bit selects the source of the Vsync for sync
processing only if Bit 7 of Register 0x14 is set to 1.
Setting Bit 6 to 0 specifies the Vsync from the input
pin; setting it to 1 selects Vsync from the sync
separator. Power-up default is 0.
Table 22. Active Vsync Select Settings
Select Result
0 Vsync
input
1
Vsync from sync separator
0x14
5
Vsync Input Polarity Override
This bit sets whether the chip selects the Vsync input
polarity or if it is specified. Setting this bit to 0 allows
the chip to automatically select the polarity of the
input Vsync. Setting this bit to 1 indicates that Bit 4 of
Register 0x14 specifies the polarity. Power-up default
is 0.
Table 23. Vsync Input Polarity Override Settings
Override Bit
Result
0
Vsync polarity determined by chip
1
Vsync polarity determined by user
Register 0x14, Bit 4
0x14
4
Input Vsync Polarity
If Bit 5 of Register 0x14 is 1, the value of this bit
specifies the polarity of the input Vsync. Setting this
bit to 0 indicates an active low Vsync; setting this bit
to 1 indicates an active high Vsync. Power-up default
is 1.
Table 24. Vsync Input Polarity Settings
Override Bit
Result
0
Vsync input polarity is negative
1
Vsync input polarity is positive
0x14
3
Vsync Output Polarity
This bit sets the polarity of the Hsync output. Setting
this bit to 0 sets the Hsync output to active low. Setting
this bit to 1 sets the Hsync output to active high.
Power-up default is 1.
Table 25. Vsync Output Polarity Settings
Vsync Output
Polarity Bit
Result
0
Vsync output polarity is negative
1
Vsync output polarity is positive
0x14
2
Vsync Filter Enable
This bit enables the Vsync filter allowing precise
placement of the Vsync with respect to the Hsync
and facilitating the correct operation of the
Hsyncs/Vsync count.
Table 26. Vsync Filter Enable
Vsync Filter Bit
Result
0
Vsync filter disabled
1
Vsync filter enabled
0x14 1
Vsync
Duration
Enable
This enables the Vsync duration block, which is
designed to be used with the Vsync filter. Setting the
bit to 0 leaves the Vsync output duration unchanged.
Setting the bit to 1 sets the Vsync output duration
based on Register 0x15. Power-up duration is 0.
Table 27. Vsync Duration Enable
Vsync Duration Bit
Result
0
Vsync output duration is unchanged
1
Vsync output duration is set by Register
0x15
0x15 7:0 Vsync
Duration
This is used to set the output duration of the Vsync,
and is designed to be used with the Vsync filter. This
is valid only if Register 0x14, Bit 1 is set to 1. Power-up
default is 10 DDR.
COAST AND CLAMP CONTROLS
0x16 7:0 Precoast
This register allows the internally generated coast
signal to be applied prior to the Vsync signal. This is
necessary in cases where pre-equalization pulses are
present. The step size for this control is one Hsync
period. For precoast to work correctly, it is necessary
for the Vsync filter (0x14, Bit 2) and sync processing
filter (Register 0x20, Bit 1) both to be either enabled or
disabled. The power-up default is 00.
0x17 7:0 Postcoast
This register allows the internally generated Coast
signal to be applied following the Vsync signal. This is
necessary in cases where postequalization pulses are
present. The step size for this control is one Hsync
period. For Postcoast to work correctly, it is necessary
for the Vsync filter (0x14, Bit 2) and sync processing
filter (0x20, Bit 1) both to be either enabled or
disabled. The power-up default is 00.
0x18 7
Coast
Source
This bit is used to select the active Coast source. The
choices are the coast input pin or Vsync. If Vsync is
selected, the additional decision of using the Vsync
input pin or the output from the sync separator needs
to be made (Register 0x14, Bits [7: 6]).
AD9984
Preliminary Technical Data
Rev. PrB | Page 34 of 45
Table 28. Coast Source Selection Settings
Select Result
0
Vsync (internal Coast)
1
COAST input pin
0x18
6
Coast Polarity Override
This register is used to override the internal circuitry
that determines the polarity of the coast signal going
into the PLL. The power-up default setting is 0.
Table 29. Coast Polarity Override Settings
Override Bit
Result
0
Coast polarity determined by chip
1
Coast polarity determined by user
0x18
5
Input Coast Polarity
This register sets the input coast polarity when Bit 6 of
Register 0x18 = 1. The power-up default setting is 1.
Table 30. Coast Polarity Settings
Coast Polarity Bit
Result
0
Coast polarity is negative
1
Coast polarity is positive
0x18 4
Clamp
Source
This bit determines the source of clamp timing. A 0
enables the clamp timing circuitry controlled by
clamp placement and clamp duration. The clamp
posi-tion and duration is counted from the leading
edge of Hsync. A 1 enables the external clamp input
pin. The three channels are clamped when the clamp
signal is active. The polarity of clamp is determined by
the clamp polarity bit. The power-up default setting
is 0.
Table 31. Clamp Source Selection Settings
Clamp Source
Result
0
Internally generated clamp
1
Externally provided clamp signal
0x18
3
Red Clamp Select
This bit determines whether the red channel is
clamped to ground or to midscale. The power-up
default setting is 0.
Table 32. Red Clamp Select Settings
Clamp Result
0
Clamp to ground
1
Clamp to midscale
0x18
2
Green Clamp Select
This bit determines whether the green channel is
clamped to ground or to midscale. The power-up
default setting is 0.
Table 33. Green Clamp Select Settings
Clamp Result
0
Clamp to ground
1
Clamp to midscale
0x18
1
Blue Clamp Select
This bit determines whether the blue channel is
clamped to ground or to midscale. The power-up
default setting is 0.
Table 34. Blue Clamp Select Settings
Clamp Result
0
Clamp to ground
1
Clamp to midscale
0x19 7:0 Clamp
Placement
An 8-bit register that sets the position of the internally
generated clamp. When EXTCLMP = 0 (Register
0x18, Bit 4), a clamp signal is generated internally, at a
position established by the clamp placement register
(Register 0x19) and for a duration set by the clamp
duration register (Register 0x1A). Clamping is started
a clamp placement count(Register 0x19) of pixel
periods after the trailing edge of Hsync. The clamp
placement may be programmed to any value between
1 and 255. A value of 0 is not supported.
The clamp should be placed during a time that the
input signal presents a stable black-level reference,
usually the back porch period between Hsync and the
image. When EXTCLMP = 1, this register is ignored.
Power-up default setting is 8.
0x1A 7:0 Clamp
Duration
An 8-bit register that sets the duration of the
internally generated clamp. When EXTCLMP = 0
(Register 0x18, Bit 4), a clamp signal is generated
internally at a position established by the clamp
placement register (and for a duration set by the
clamp duration register). Clamping begins a clamp
placement count (Register 0x19) of pixel periods after
the trailing edge of Hsync. The clamp duration may be
programmed to any value between 1 and 255. A value
of 0 is not supported.
For the best results, the clamp duration should be set
to include the majority of the black reference signal
time that follows the Hsync signal trailing edge. Insuf-
ficient clamping time can produce brightness changes
at the top of the screen, and a slow recovery from large
changes in the average picture level (APL), or bright-
ness. When EXTCLMP = 1, this register is ignored.
Power-up default setting is 20 DDR.
Preliminary Technical Data
AD9984
Rev. PrB | Page 35 of 45
0x1B
7
Clamp Polarity Override
This bit is used to override the internal circuitry that
determines the polarity of the clamp signal. The
power-up default setting is 0.
Table 35. Clamp Polarity Override Settings
Override Bit
Result
0
Clamp Polarity Determined by Chip
1
Clamp Polarity Determined by User
Register 0x1B, Bit 6
0x1B
6
Input Clamp Polarity
This bit indicates the polarity of the clamp signal only
if Bit 7 of Register 0x1B = 1. The power-up default
setting is 1.
Table 36. Clamp Polarity Override Settings
CLMPOL Result
0 Active
low
1 Active
high
0x1B 5
Auto-Offset
Enable
This bit selects between auto-offset mode and manual
offset mode (auto-offset disabled) (See the section on
auto-offset operation). The power-up default setting
is 0.
Table 37. Auto-Offset Settings
Auto-Offset Result
0
Auto-offset is disabled
1
Auto-offset is enabled (manual offset mode)
0x1B 4:3 Auto-Offset
Update
Frequency
These bits control how often the auto-offset circuit is
updated (if enabled). Updating every 64 Hsyncs is
recommended. The power-up default setting is 11.
Table 38. Auto-Offset Update Mode
Clamp Update
Result
00
Update offset every clamp period
01
Update offset every 16 clamp periods
10
Update offset every 64 clamp periods
11
Update offset every Vsync periods
0x1B 2-0
Must be written to 011 for proper operation.
SOG CONTROL
0x1D
7:3
SOG Comparator Threshold
This register allows the comparator threshold of the
SOG slicer to be adjusted. This register adjusts it in
steps of 8 mV, with the minimum setting equaling
8 mV and the maximum setting equaling 256 mV. The
power-up default setting is 15 DDR and corresponds
to a threshold value of 128 mV.
0x1D
2
SOG Output Polarity
This bit sets the polarity of the SOGout signal. The
power-up default setting is 0.
Table 39. SOGout Polarity Settings
SOGOUT Result
0 Active
low
1 Active
high
0x1D
1:0
SOG Output Select
These register bits control what is output on the
SOGout pin. Options are the raw SOG from the slicer
(this is the unprocessed SOG signal produced from
the sync slicer), the raw Hsync, the regenerated sync
from the sync filter which can generate missing syncs
either due to coasting or drop-out, or finally the
filtered sync which excludes extraneous syncs not
occurring within the sync filter window. The power-
up default setting is 0.
Table 40. SOGout Polarity Settings
SOGOUT Select
Function
00
Raw SOG from sync slicer (SOG0 or SOG1)
01
Raw Hsync (Hsync0 or Hsync1)
10
Regenerated Sync from sync filter
11
Filtered sync from sync filter
INPUT AND POWER CONTROL
0x1E
7
Channel Select Override
This bit provides an override to the automatic input
channel selection. Power-up default setting is 0.
Table 41. Channel Source Override
Override Result
0
Channel input source determined by chip
1
Channel input source determined by user
Register 0x1E, Bit 6
0x1E 6
Channel
Select
This bit selects the active input channel if
Register 0x1E, bit 7 = 1 . This selects between
Channel 0 data and syncs or Channel 1 data and
syncs. Power-up default setting is 0.
Table 42. Channel Select
Channel Select
Result
0
Channel 0 data and syncs are selected
1
Channel 1 data and syncs are selected
0x1E 5
Programmable
Bandwidth
This bit selects between a low or high input band-
width. It is useful in limiting noise for lower frequency
inputs. The power-up default setting is 1. Low analog
input bandwidth is ~100 MHz; high analog input
AD9984
Preliminary Technical Data
Rev. PrB | Page 36 of 45
bandwidth is ~200 MHz.
Table 43. Input Bandwidth Select
Input Bandwidth
Result
0
Low analog input bandwidth
1
High analog input bandwidth
0x1E
4
Power-Down Control Select
This bit determines whether power-down is con-
trolled manually or automatically by the chip. If
automatic control is selected (Register 0x1E, Bit 4),
the AD9984's decision is based on the status of the
sync detect bits (Register 0x24, Bits 2, 3, 6, and 7). If
either an Hsync or a sync-on-green input is detected
on any input, the chip powers up or powers down.
For manual control, the AD9984 allows the flexibility
of control through both a dedicated pin and a register
bit. The dedicated pin allows a hardware watchdog
circuit to control power-down, while the register bit
allows power-down to be controlled by software. With
manual power-down control, the polarity of the
powerdown pin must be set (0x1E, Bit 2) whether it is
used or not. If unused, it is recommended to set the
polarity to active high and hardwire the pin to ground
with a 10 k resistor.
Table 44. Auto Power-Down Select
Power-Down Select
Result
0
Manual power-down control
(User determines power-down)
1
Auto power-down control
(Chip determines power-down)
0x1E 3
Power-Down
This bit is used to manually place the chip in power-
down mode. It is only used if manual power-down
control is selected (see Bit 4 above). Both the state of
this register bit and the power-down pin (Pin 17)
are used to control manual power-down. (See the
Power Management
section for more details on
power-down.)
Table 45. Power-Down Settings
Power-Down Select
Pin 17
Result
0 0
Normal
operation
1 X
Power-down
0x1E 2
Power-Down
Polarity
This bit defines the polarity of the power-down pin
(Pin 17). It is only used if manual power-down
control is selected (see Bit 4 above).
Table 46. Power-Down Pin Polarity
Select Result
0
Power-down pin is active low
1
Power-down pin is active high
0x1E
1
Power-Down Fast Switching Control
This bit controls a special fast switching mode. With
this bit the AD9984 can stay active during power-
down and only put the outputs in high impedance.
This option is useful when the data outputs from two
chips are connected on a PCB and the user wants to
switch instantaneously between the two.
Table 47. Power-Down Fast Switching Control
Fast Switching Control
Result
0
Normal power-down operation
1
The chip stays powered up and the
outputs are put in high impedance
mode.
0x1E
0
SOGOUT High Impedance Control
This bit controls whether the SOGOUT output pin is
in high impedance or not, when in power-down
mode. In most cases, SOGOUT is not put in high
impedance during normal operation. It is usually
needed for sync detection by the graphics controller.
The option to put SOGOUT in high impedance is
included mainly to allow for factory testing modes.
Table 42. SOGOUT High Impedance Control
SOGOUT Control
Result
0
The SOGOUT output operates as
normal during power-down.
1
The SOGOUT output is in high
impedance during power-down.
OUTPUT CONTROL
0x1F 7:5 Output
Mode
These bits choose between three options for the
output mode. In 4:4:4 mode, RGB is standard. In 4:2:2
mode, YCbCr is standard, which allows a reduction in
the number of output pins from 30 to 20. In 4:4:4
DDR output mode, the data is in RGB mode, but
changes on every clock edge. The power-up default
setting is 100.
Table 43. Output Mode
Output Mode
Result
100
4:4:4 RGB mode
101
4:2:2 YCbCr mode
110
4:4:4 DDR mode
0x1F
4
Primary Output Enable
This bit places the primary output in active or high
impedance mode. The power-up default setting is 1.
Table 44. Primary Output Enable
Select Result
0
Primary output is in high impedance
mode
1
Primary output is enabled
Preliminary Technical Data
AD9984
Rev. PrB | Page 37 of 45
0x1F
3
Secondary Output Enable
This bit places the secondary output in active or high
impedance mode.
The secondary output is designated when using either
4:2:2 or 4:4:4-d (DDR). In these modes, the data on
the blue output channel is the secondary output while
the output data on the red and green channels are the
primary output. Secondary output is always a DDR
YCbCr data mode. See the Output Formatter section
and Table 11. The power-up default setting is 0.
Table 45. Secondary Output Enable
Select Result
0
Secondary output is in high impedance mode
1
Secondary output is enabled
0x1F
2:1
Output Drive Strength
These two bits select the drive strength for all the
high-speed digital outputs (except Vsout, A0, and the
O/E field). Higher drive strength results in faster
rise/fall times and in general makes it easier to capture
data. Lower drive strength results in slower rise/fall
times and helps to reduce EMI and digitally generated
power supply noise. The power-up default setting
is 10.
Table 46. Output Drive Strength
Output Drive
Result
00
Low output drive strength
01
Medium low output drive strength
10
Medium high output drive strength
11
High output drive strength
0x1F
0
Output Clock Invert
This bit allows inversion of the output clock. The
power-up default setting is 0.
Table 47. Output Clock Invert
Select Result
0
Noninverted pixel clock
1
Inverted pixel clock
0x20 7:6 Output
Clock
Select
These bits allow selection of optional output clocks
such as a fixed 40 MHz clock, a 2× clock, a 90° phase-
shifted clock, or the normal pixel clock. The power-up
default setting is 00.
Table 48. Output Clock Select
Select Result
00 Pixel
clock
01
90° phase-shifted pixel clock
10
2× pixel clock
11
40 MHz internal clock
0x20
5
Output High Impedance
This bit puts all outputs (except SOGOUT) in a high impedance
state. The power-up default setting is 0.
Table 49. Output High Impedance
Select Result
0 Normal
outputs
1
All outputs (except SOGOUT) in high impedance
mode
0x20
4
SOG High Impedance
This bit allows the SOGOUT pin to be placed in high
impedance mode. The power-up default setting is 0.
Table 50. SOGOUT High Impedance
Select Result
0
Normal SOG output
1
SOGOUT pin is in high impedance mode
0x20
3
Field Output Polarity
This bit sets the polarity of the field output bit. The
power-up default setting is 1.
Table 51. Field Output Polarity
Select Result
0
Active low = even field; active high = odd field
1
Active low = odd field; active high = even field
SYNC PROCESSING
0x20
2
PLL Sync Filter
This bit selects which signal the PLL uses. It can select
between either raw Hsync or SOG or filtered versions.
The filtering of the Hsync and SOG can eliminate
nearly all extraneous transitions which have tradi-
tionally caused PLL disruption. The power-up default
setting is 0.
Table 52. PLL Sync Filter Enable
Select Result
0
PLL uses raw Hsync or SOG inputs
1
PLL uses filtered Hsync or SOG inputs
0x20
1
Sync Processing Input Source
This bit selects whether the sync processor uses a raw
sync or a regenerated sync for the following functions:
Coast, H/V count, field detection and Vsync duration
counts. Using the regenerated sync is recommended.
Table 53. SP Filter Enable
Select Result
0
Sync processing uses raw Hsync or SOG
1
Sync processing uses the internally regenerated
Hsync
AD9984
Preliminary Technical Data
Rev. PrB | Page 38 of 45
0x21
7:0
Must be set to default
0x22
7:0
Must be set to default
0x23
7:0
Sync Filter Window Width
This 8-bit register sets the window of time for the regenerated
Hsync leading edge (in 25 nS steps) and that sync pulses are
allowed to pass through. Therefore with the default value of 10,
the window width is ±250 nS. The goal is to set the window
width so that extraneous pulses are rejected. (see the Sync
Processing section). As in the sync separator threshold, the
25 nS multiplier value is somewhat variable. The maximum
variability over all operating conditions is ±20% (20 nS
to 30 nS).
DETECTION STATUS
0x24 7
Hsync0
Detection
Bit
This bit is used to indicate when activity is detected on
the Hsync0 input pin. If Hsync is held high or low,
activity is not detected. The sync processing block
diagram shows where this function is implemented.
0 = Hsync0 not active. 1 = Hsync 0 is active.
Table 54. Hsync0 Detection Results
Detect Result
0
No activity detected
1 Activity
detected
0x24 6
Hsync1
Detection
Bit
This bit is used to indicate when activity is detected on
the Hsync1 input pin. If Hsync is held high or low,
activity is not detected. The sync processing block
diagram shows where this function is implemented.
0 = Hsync1 not active. 1 = Hsync 1 is active.
Table 55. Hsync1 Detection Results
Detect Result
0
No activity detected
1 Activity
detected
0x24 5
Vsync0
Detection
Bit
This bit is used to indicate when activity is detected on
the Vsync0 input pin. If Vsync is held high or low,
activity is not detected. The sync processing block
diagram shows where this function is implemented.
0 = Vsync 0 not active. 1 = Vsync 0 is active.
Table 56. Vsync0 Detection Results
Detect Result
0
No activity detected
1 Activity
detected
0x24 4
Vsync1
Detection
Bit
This bit is used to indicate when activity is detected on
the Vsync1 input pin. If Vsync is held high or low,
activity is not detected. The sync processing block
diagram shows where this function is implemented.
0 = Vsync 1 not active. 1 = Vsync 1 is active.
Table 57. Vsync1 Detection Results
Detect Result
0
No activity detected
1 Activity
detected
0x24 3
SOG0
Detection
Bit
This bit is used to indicate when activity is detected on
the SOG0 input pin. If SOG is held high or low,
activity is not detected. The sync processing block
diagram shows where this function is implemented.
0 = SOG 0 not active. 1 = SOG 0 is active.
Table 58. SOG0 Detection Results
Detect Result
0
No activity detected
1 Activity
detected
0x24 2
SOG1
Detection
Bit
This bit is used to indicate when activity is detected on
the SOG1 input pin. If SOG is held high or low,
activity is not detected. The sync processing block
diagram shows where this function is implemented.
0 = SOG 1 not active. 1 = SOG 1 is active.
Table 59. SOG1 Detection Results
Detect Result
0
No activity detected
1 Activity
detected
0x24
1
Coast Detection Bit
This bit detects activity on the EXTCLK/EXTCOAST
pin. It indicates that one of the two signals is active,
but it doesn't indicate which one. A dc signal is
not detected.
Table 60. Coast Detection Result
Detect Result
0
No activity detected
1 Activity
detected
0x24 0
Clamp
Detection
Bit
This bit is used to indicate when activity is detected on
the external clamp pin. If external clamp is held high
or low, activity is not detected.
Table 61. Clamp Detection Results
Detect Result
0
No activity detected
1 Activity
detected
Preliminary Technical Data
AD9984
Rev. PrB | Page 39 of 45
POLARITY STATUS
0x25 7
Hsync0
Polarity
Indicates the polarity of Hsync0 input.
Table 62. Detected Hsync0 Polarity Results
Detect Result
0
Hsync polarity is negative
1
Hsync polarity is positive
0x25 6
Hsync1
Polarity
Indicates the polarity of Hsync1 input.
Table 63. Detected Hsync1 Polarity Results
Detect Result
0
Hsync polarity is negative
1
Hsync polarity is positive
0x25 5
Vsync0
Polarity
Indicates the polarity of Vsync0 input.
Table 64. Detected Vsync0 Polarity Results
Detect Result
0
Vsync polarity is negative
1
Vsync polarity is positive
0x25 4
Vsync1
Polarity
Indicates the polarity of Vsync1 input.
Table 65. Detected Vsync1 Polarity Results
Detect Result
0
Vsync polarity is negative
1
Vsync polarity is positive
0x25 3
Coast
Polarity
Indicates the polarity of the external Coast signal.
Table 66. Detected Coast Polarity Results
Detect Result
0
Coast polarity is negative
1
Coast polarity is positive
0x25 2
Clamp
Polarity
Indicates the polarity of the clamp signal.
Table 67. Detected Clamp Polarity Results
Detect Result
0
Clamp polarity is negative
1
Clamp polarity is positive
0x25
1
Extraneous Pulses Detection
A second output from the Hsync filter, this status bit tells
whether extraneous pulses are present on the incoming sync
signal. Often extraneous pulses are used for copy protection, so
this status bit can be used for this purpose.
Table 68. Equalization Pulse Detect Bit
Detect Result
0
No equalization pulses detected during active
Hsync
1 Equalization
pulses
detected during active Hsync
HSYNC COUNT
0x26 7:0 Hsyncs/Vsync
MSB
The eight MSBs of the 12-bit counter that reports the
number of Hsyncs/Vsync on the active input. This is
useful for determining the mode and is an aid in
setting the PLL divide ratio.
0x27 7:4 Hsyncs/Vsync
LSBs
The four LSBs of the 12-bit counter that reports the
number of Hsyncs/Vsync on the active input.
Test Registers
0x28
7:0
Test Register 0
Must be written to 0xBF for proper operation.
0x29
7:0
Test Register 1
Must be written to 0x00 for proper operation.
0x2A
7:0
Test Register 2
Read only bits for future use.
0x2B
7:0
Test Register 3
Read only bits for future use.
0x2C
7:0
Test Register 4
Must be written to 0x00 for proper operation.
0x2C 4
Auto-Offset
Hold
A bit for controlling whether the auto-offset function
runs continuously or runs once and holds the result.
Continuous updates are recommended because it
allows the AD9984 to compensate for drift-over time,
temperature, etc. If one-time updates are preferred,
these should be performed every time the part is
powered up and when there is a mode change. To do a
one-time update, first auto-offset must be enabled
(0x1B, Bit 5). Next, this bit (auto-offset hold) must
first be set to 1 to let the auto-offset function operate
and settle to a final value. Auto-offset hold should
then be set to 0 to hold the offset values that the auto
circuitry calculates. The AD9984's auto-offset circuit's
maxi-mum settle time is 10 updates. For example, if
the update frequency is set to once every 64 Hsyncs,
then the maximum settling time would be 640 Hsyncs
(10 × 64 Hsyncs).
AD9984
Preliminary Technical Data
Rev. PrB | Page 40 of 45
Table 69. Auto-Offset Hold
Select Result
0
Disables auto-offset updates and holds the
current auto-offset values
1
Allows auto-offset to update continuously
0x2C 3:0
Must be written to 0x0 for proper operation.
0x2D
7:0
Test Register 5
Read/write bits for future use. Must be written to
0xE8 for proper operation.
0x2E
7:0
Test Register 6
Read/write bits for future use. Must be written to
0xE0 for proper operation.
0x3C 7:4 Test
Bits
Must be set to 0x0 for proper operation.
0x3C 3
Auto
Gain
Matching
Hold
A bit for controlling whether the Auto Gain Matching
function runs continuously or runs once and holds the result.
Continuous updates are recommended because it allows the
AD9984 to compensate for drift over time, temperature, etc. If
one-time updates are preferred, these should be performed
every time the part is powered up and when there is a mode
change. To do a one-time update, first Auto Gain Matching
must be enabled (3Ch, bit 2). Next, this bit (Auto Gain
Matching Hold) must first be set to "1" to let the Auto Gain
Matching function operate and settle to a final value. The Auto
Gain Matching Hold bit should then be set to "0" to hold the
gain values that the auto circuitry calculates. The AD9984's
Auto Gain Matching circuit's maximum settle time is 10
updates. For example, if the update frequency is set to once
every 64 Hsyncs, then the maximum settling time would be 640
Hsyncs (10 x 64 Hsyncs).
Table 70.
Select Result
0
Disables Auto Gain updates and
holds the current Auto Offset
values.
1
Allows Auto Gain to update
continuously
The power-up default setting is `0'
0x3C
2:0 Auto Gain Matching Enable
These bits enable or disable the Auto Gain Matching
function. When set to `000', the Auto Gain Matching
function is disabled; when set to `110' the Auto Gain
Matching function is enabled.
Table 71.
Select Result
000
Auto Gain Matching Disabled
110
Auto Gain Matching Enabled.
Preliminary Technical Data
AD9984
Rev. PrB | Page 41 of 45
TWO-WIRE SERIAL CONTROL PORT
A two-wire serial interface control interface is provided. Up to
two AD9984 devices may be connected to the two-wire serial
interface, with each device having a unique address.
The two-wire serial interface comprises a clock (SCL) and a bi-
directional data (SDA) pin. The analog flat panel interface acts
as a slave for receiving and transmitting data over the serial
interface. When the serial interface is not active, the logic levels
on SCL and SDA are pulled high by external pull-up resistors.
Data received or transmitted on the SDA line must be stable for
the duration of the positive-going SCL pulse. Data on SDA must
change only when SCL is low. If SDA changes state while SCL is
high, the serial interface interprets that action as a start or stop
sequence.
The following are the five components to serial bus operation:
·
Start signal
·
Slave address byte
·
Base register address byte
·
Data byte to read or write
·
Stop signal
When the serial interface is inactive (SCL and SDA are high),
communications are initiated by sending a start signal. The start
signal is a high-to-low transition on SDA while SCL is high.
This signal alerts all slaved devices that a data transfer sequence
is coming.
The first eight bits of data transferred after a start signal
comprise a 7-bit slave address (the first seven bits) and a single
R/W\ bit (the eighth bit). The R/W\ bit indicates the direction
of data transfer, read from 1 or write to 0 on the slave device. If
the transmitted slave address matches the address of the device
(set by the state of the Serial A0 address [SA0] input pin in
Table 70), the AD9984 acknowledges the match by bringing
SDA low on the 9th SCL pulse. If the addresses do not match,
the AD9984 does not acknowledge it.
Table 70. Serial Port Addresses
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
A6
(MSB) A5 A4 A3 A2 A1 A0
1
0 0 1 1 0 0
1
0 0 1 1 0 1
DATA TRANSFER VIA SERIAL INTERFACE
For each byte of data read or written, the MSB is the first bit in
the sequence.
If the AD9984 does not acknowledge the master device during a
write sequence, the SDA remains high so the master can gener-
ate a stop signal. If the master device does not acknowledge the
AD9984 during a read sequence, the AD9984 interprets this as
end of data. The SDA remains high so the master can generate a
stop signal.
Writing data to specific control registers of the AD9984 requires
that the 8-bit address of the control register of interest be writ-
ten after the slave address has been established. This control
register address is the base address for subsequent write opera-
tions. The base address auto-increments by one for each byte of
data written after the data byte intended for the base address. If
more bytes are transferred than there are available addresses,
the address will not increment and remain at its maximum
value of 0x2E. Any base address higher than 0x2E will not pro-
duce an acknowledge signal. Data are read from the control
registers of the AD9984 in a similar manner. Reading requires
two data transfer operations:
The base address must be written with the R/W bit of the slave
address byte low to set up a sequential read operation. Reading
(the R/W\ bit of the slave address byte high) begins at the
previously established base address. The address of the read
register auto-increments after each byte is transferred.
To terminate a read/write sequence to the AD9984, a stop signal
must be sent. A stop signal comprises a low-to-high transition
of SDA while SCL is high.
A repeated start signal occurs when the master device driving
the serial interface generates a start signal without first genera-
ting a stop signal to terminate the current communication. This
is used to change the mode of communication (read, write)
between the slave and master without releasing the serial
interface lines.
SDA
SCL
t
BUFF
t
STAH
t
DHO
t
DSU
t
DAL
t
DAH
t
STASU
t
STOSU
04739-011
Figure 17. Serial Port Read/Write Timing
AD9984
Preliminary Technical Data
Rev. PrB | Page 42 of 45
Serial Interface Read/Write Examples
Write the following to one control register:
·
Start signal
·
Slave address byte (R/W\bit = low)
·
Base address byte
·
Data byte to base address
·
Stop signal
Write to four consecutive control registers:
·
Start signal
·
Slave address byte (R/W\bit = low)
·
Base address byte
·
Data byte to base address
·
Data byte to (base address + 1)
·
Data byte to (base address + 2)
·
Data byte to (base address + 3)
·
Stop signal
Read from one control register:
·
Start signal
·
Slave address byte (R/W\bit = low)
·
Base address byte
·
Start signal
·
Slave address byte (R/W\ bit = high)
·
Data byte from base address
·
Stop signal
Read from four consecutive control registers:
·
Start signal
·
Slave address byte (R/W\bit = low)
·
Base address byte
·
Start signal
·
Slave address byte (R/W\bit = high)
·
Data byte from base address
·
Data byte from (base address + 1)
·
Data byte from (base address + 2)
·
Data byte from (base address + 3)
·
Stop signal
BIT 7
ACK
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
SDA
SCL
04739-012
Figure 18. Serial Interface--Typical Byte Transfer
I2C BUS HARDWARE CONSIDERATIONS
Components that share the I2C bus with the AD9984 may have
strict 3.3V logic level requirements. Due to the ESD diode
structure of the AD9984's SDA and SCL lines, the AD9984 will
clamp the I2C lines to approximately 2.4V. In addition to the
I2C lines, the same condition can be generated for the
PWRDN, CLAMP and EXTCLK/COAST pins but these signals
should not require level shifting.
Solution
The circuit in Figure provides isolation that allows the I2C bus
to maintain 3.3V logic levels while allowing the AD9984 to
operate at it's preferred 1.8V logic level. The circuit is required
for both the SDA and SCL. Note that 3.3V is the 3.3-volt
supply for the master I2C device and VD is the 1.8-volt analog
supply of the AD9984.
Current densities on the PWRDN, CLAMP and
EXTCLK/COAST pins can be handled by the ESD diode
structure. Adding a 1k resistor in series with these pins is
acceptable as a precautionary measure but not required.
Figure 19. I2C FET Buffer.
Preliminary Technical Data
AD9984
Rev. PrB | Page 43 of 45
PCB LAYOUT RECOMMENDATIONS
The AD9984 is a high-precision, high-speed analog device.
To achieve the maximum performance from the part, it is
impor-tant to have a well laid-out board. The Analog Interface
Inputs section provides a guide for designing a board using
the AD9984.
Analog Interface Inputs
Using the following layout techniques on the graphics inputs is
extremely important:
1.
Minimize the trace length running into the graphics
inputs. This is accomplished by placing the AD9984 as
close as possible to the graphics VGA connector. Long
input trace lengths are undesirable because they pick up
noise from the board and other external sources.
2.
Place the 75 termination resistors (see Figure 3) as close
as possible to the AD9984 chip. Any additional trace length
between the termination resistors and the input of the
AD9984 increases the magnitude of reflections, which
corrupts the graphics signal.
3.
Use 75 matched impedance traces. Trace impedances
other than 75 also increases the chance of reflections.
4.
The AD9984 has a very high input bandwidth, (200 MHz).
While this is desirable for acquiring a high resolution PC
graphics signal with fast edges, it also means that it
captures any high frequency noise present. Therefore, it is
important to reduce the amount of noise that gets coupled
to the inputs. Avoid running any digital traces near the
analog inputs.
5.
Due to the high bandwidth of the AD9984, sometimes
low-pass filtering the analog inputs can help to reduce
noise. (For many applications, filtering is unnecessary.)
Experiments have shown that placing a ferrite bead in
series prior to the 75 termination resistor is helpful in
filtering excess noise. Specifically, the Fair-Rite
#2508051217Z0 was used, but an application could work
best with a different bead value. Alternatively, placing a 100
to 120 resistor between the 75 termination resistor
and the input coupling capacitor is beneficial.
Power Supply Bypassing
It is recommended to bypass each power supply pin with a
0.1 F capacitor. The exception is where two or more supply
pins are adjacent to each other. For these groupings of
powers/grounds, it is only necessary to have one bypass
capacitor. The fundamental idea is to have a bypass capacitor
within about 0.5 cm of each power pin. Also, avoid placing the
capacitor on the opposite side of the PC board from the
AD9984, since that interposes resistive vias in the path.
The bypass capacitors should be physically located between the
power plane and the power pin. Current should flow from the
power plane to the capacitor to the power pin. Do not make the
power connection between the capacitor and the power pin.
Placing a via underneath the capacitor pads, down to the power
plane, is generally the best approach.
It is particularly important to maintain low noise and good
stability of the PV
D
(the clock generator supply). Abrupt
changes in PV
D
can result in similarly abrupt changes in
sampling clock phase and frequency. This can be avoided by
careful attention to regulation, filtering, and bypassing. It is
highly desirable to provide separate regulated supplies for each
of the analog circuitry groups (V
D
and PV
D
).
Some graphic controllers use substantially different levels of
power when active (during active picture time) and when idle
(during horizontal and vertical sync periods). This can result in
a measurable change in the voltage supplied to the analog
supply regulator, which can in turn produce changes in the
regulated analog supply voltage. This can be mitigated by
regulating the analog supply, or at least PV
D
, from a different,
cleaner, power source (for example, from a 12 V supply).
It is also recommended to use a single ground plane for the
entire board. Experience has repeatedly shown that the noise
performance is the same or better with a single ground plane.
Using multiple ground planes can be detrimental because each
separate ground plane is smaller and long ground loops can
result.
In some cases, using separate ground planes is unavoidable. For
those cases, it is recommended to at least place a single ground
plane under the AD9984. The location of the split should be at
the receiver of the digital outputs. In this case it is even more
important to place components wisely because the current
loops will be much longer, (current takes the path of least
resistance). An example of a current loop is power plane to
AD9984 to digital output trace to digital data receiver to digital
ground plane to analog ground plane.
PLL
Place the PLL loop filter components as close to the FILT pin as
possible. Do not place any digital or other high frequency traces
near these components. Use the values suggested in the data-
sheet with 10% tolerances or less.
Outputs (Both Data and Clocks)
Try to minimize the trace length that the digital outputs have to
drive. Longer traces have higher capacitance and require more
instantaneous current to drive, which creates more internal
digital noise. Shorter traces reduce the possibility of reflections.
AD9984
Preliminary Technical Data
Rev. PrB | Page 44 of 45
Adding a series resistor of value 50 to 200 can suppress
reflections, reduce EMI, and reduce the current spikes inside of
the AD9984. If series resistors are used, place them as close to
the AD9984 pins as possible, (although try not to add vias or
extra length to the output trace to get the resistors closer).
If possible, limit the capacitance that each digital output drives
to less than 10 pF. This is easily accomplished by keeping traces
short and by connecting the outputs to only one device.
Loading the outputs with excessive capacitance increases the
current transients inside of the AD9984 and creates more digital
noise on its power supplies.
Digital Inputs
Digital inputs on the AD9984 (Hsync0, Hsync1, Vsync0,
Vsync1, SOGIN0, SOGIN1, SDA, SCL and CLAMP) were
designed to work with 3.3 V signals, but are tolerant of 5.0 V
signals. Therefore, no extra components need to be added if
using 5.0 V logic.
Any noise that gets onto the Hsync input trace adds jitter to the
system. Therefore, minimize the trace length and do not run
any digital or other high frequency traces near it.
REFERENCE Bypass
The AD9984 has three reference voltages that must be bypassed
for proper operation of the input PGA. REFLO and REFHI are
connected to each other through a 10 F capacitor. These refer-
ences are used by the input PGA circuitry to assure the greatest
stability. Place them as close to the AD9984 pin as possible.
Make the ground connection as short as possible.
Preliminary Technical Data
AD9984
Rev. PrB | Page 45 of 45
OUTLINE DIMENSIONS
1.45
1.40
1.35
0.15
0.05
61
60
1
80
20
41
21
40
TOP VIEW
(PINS DOWN)
PIN 1
SEATING
PLANE
VIEW A
1.60
MAX
0.75
0.60
0.45
0.20
0.09
0.10 MAX
COPLANARITY
VIEW A
ROTATED 90° CCW
SEATING
PLANE
10°

3.5°
14.00
BSC SQ
16.00
BSC SQ
0.65
BSC
0.38
0.32
0.22
COMPLIANT TO JEDEC STANDARDS MS-026-BEC
Figure20. 80-Lead Low Profile Quad Flat Pack [LQFP]
(ST-80-2)
Dimensions shown in millimeters
ORDERING GUIDE
Model
Temperature Range
Package Description
Package
AD9984KSTZ-110
0°C to 70°C
LQFP
ST-80
AD9984KSTZ-140
0°C to 70°C
LQFP
ST-80
AD9984KSTZ-170
0°C to 70°C
LQFP
ST-80
AD9984/PCB
25°C
Evaluation Kit
Purchase of licensed I
2
C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the
purchaser under the Philips I
2
C Patent Rights to use these components in an I
2
C system, provided that the system conforms to the I
2
C
Standard Specification as defined by Philips.
© 2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered
trademarks are the property of their respective owners.
PR05839-0-1/06(PrB)