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Part Number AD9835

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AD9835 Data Sheet
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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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
AD9835
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
50 MHz CMOS
Complete DDS
FUNCTIONAL BLOCK DIAGRAM
IOUT
COMP
REFIN
FS ADJUST
REFOUT
AGND
AVDD
DGND
DVDD
MCLK
PSEL0 PSEL1
12
AD9835
ON-BOARD
REFERENCE
10-BIT
DAC
PHASE0 REG
PHASE1 REG
PHASE2 REG
PHASE3 REG
FULL-SCALE
CONTROL
COS
ROM
PHASE
ACCUMULATOR
(32 BIT)
MUX
FREQ0 REG
FREQ1 REG
MUX
16-BIT DATA REGISTER
SYNC
FSELECT
FSELECT
BIT
SELSRC
SYNC
8 LSBs
8 MSBs
DECODE LOGIC
FSYNC
SCLK
SDATA
SERIAL REGISTER
CONTROL REGISTER
FSELECT/PSEL REGISTER
DEFER REGISTER
SYNC
SYNC
SELSRC
PSEL0
BIT
PSEL1
BIT
FEATURES
5 V Power Supply
50 MHz Speed
On-Chip COS Look-Up Table
On-Chip 10-Bit DAC
Serial Loading
Power-Down Option
200 mW Power Consumption
16-Lead TSSOP
APPLICATIONS
DDS Tuning
Digital Demodulation
GENERAL DESCRIPTION
The AD9835 is a numerically controlled oscillator employing
a phase accumulator, a COS Look-Up Table and a 10-bit
D/A converter integrated on a single CMOS chip. Modulation
capabilities are provided for phase modulation and frequency
modulation.
Clock rates up to 50 MHz are supported. Frequency accuracy
can be controlled to one part in 4 billion. Modulation is ef-
fected by loading registers through the serial interface. A
power-down bit allows the user to power down the AD9835 when
it is not in use, the power consumption being reduced to 1.75 mW.
The part is available in a 16-lead TSSOP package.
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AD9835­SPECIFICATIONS
1
(V
DD
= +5 V
5%; AGND = DGND = 0 V; T
A
= T
MIN
to T
MAX
; REFIN = REFOUT;
R
SET
= 3.9 k ; R
LOAD
= 300
for IOUT, unless otherwise noted)
Parameter
AD9835B
Units
Test Conditions/Comments
SIGNAL DAC SPECIFICATIONS
Resolution
10
Bits
Update Rate (f
MAX
)
50
MSPS nom
IOUT Full Scale
4
mA
nom
4.75
mA max
Output Compliance
1.35
V max
DC Accuracy
Integral Nonlinearity
±
1
LSB typ
Differential Nonlinearity
±
0.5
LSB typ
DDS SPECIFICATIONS
2
Dynamic Specifications
Signal-to-Noise Ratio
50
dB min
f
MCLK
= 50 MHz, f
OUT
= 1 MHz
Total Harmonic Distortion
­52
dBc max
f
MCLK
= 50 MHz, f
OUT
= 1 MHz
Spurious Free Dynamic Range (SFDR)
3
f
MCLK
= 6.25 MHz, f
OUT
= 2.11 MHz
Narrow Band (
±
50 kHz)
­72
dBc min
Wide Band (
±
2 MHz)
­50
dBc min
Clock Feedthrough
­60
dBc typ
Wake-Up Time
1
ms typ
Power-Down Option
Yes
VOLTAGE REFERENCE
Internal Reference @ +25
°
C
1.21
V typ
T
MIN
to T
MAX
1.21
±
7%
V min/max
REFIN Input Impedance
10
M
typ
Reference TC
100
ppm/
°
C typ
REFOUT Output Impedance
300
typ
LOGIC INPUTS
V
INH
, Input High Voltage
DVDD ­ 0.9
V
min
V
INL
, Input Low Voltage
0.9
V
max
I
INH
, Input Current
10
µ
A
max
C
IN
, Input Capacitance
10
pF
max
POWER SUPPLIES
f
MCLK
= 50 MHz
AVDD
4.75/5.25
V
min/V
max
DVDD
4.75/5.25
V
min/V
max
I
AA
5
mA
max
I
DD
2.5 + 0.33/MHz
mA typ
I
AA
+ I
DD
4
40
mA
max
Low Power Sleep Mode
0.35
mA max
NOTES
1
Operating temperature range is as follows: B Version: ­40
°
C to +85
°
C.
2
100% production tested.
3
f
MCLK
= 6.25 MHz, Frequency Word = 5671C71C HEX, f
OUT
= 2.11 MHz.
4
Measured with the digital inputs static and equal to 0 V or DVDD. The AD9835 is tested with a capacitive load of 50 pF. The part can be operated with higher
capacitive loads, but the magnitude of the analog output will be attenuated. See Figure 5.
Specifications subject to change without notice.
IOUT
COMP
REFIN
FS
ADJUST
REFOUT
12
AD9835
ON-BOARD
REFERENCE
10-BIT
DAC
COS
ROM
FULL-SCALE
CONTROL
300
50pF
R
SET
3.9k
10nF
10nF
AVDD
Figure 1. Test Circuit with Which Specifications Are Tested
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AD9835
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TIMING CHARACTERISTICS
(V
DD
= +5 V 5%; AGND = DGND = 0 V, unless otherwise noted)
Limit at
T
MIN
to T
MAX
Parameter
(B Version)
Units
Test Conditions/Comments
t
1
20
ns min
MCLK Period
t
2
8
ns min
MCLK High Duration
t
3
8
ns min
MCLK Low Duration
t
4
50
ns min
SCLK Period
t
5
20
ns min
SCLK High Duration
t
6
20
ns min
SCLK Low Duration
t
7
15
ns min
FSYNC to SCLK Falling Edge Setup Time
t
8
20
ns min
FSYNC to SCLK Hold Time
SCLK ­ 5
ns max
t
9
15
ns min
Data Setup Time
t
10
5
ns min
Data Hold Time
t
11
8
ns min
FSELECT, PSEL0, PSEL1 Setup Time Before MCLK Rising Edge
t
11A
1
8
ns min
FSELECT, PSEL0, PSEL1 Setup Time After MCLK Rising Edge
NOTES
1
See Pin Description section.
Guaranteed by design but not production tested.
MCLK
t
2
t
1
t
3
Figure 2. Master Clock
SCLK
FSYNC
SDATA
t
5
t
4
t
6
t
7
t
8
t
10
t
9
D15
D14
D2
D1
D0
D15
D14
Figure 3. Serial Timing
t
11A
t
11
VALID DATA
VALID DATA
VALID DATA
MCLK
FSELECT
PSEL0, PSEL1
Figure 4. Control Timing
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AD9835
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ABSOLUTE MAXIMUM RATINGS*
(T
A
= +25
°
C unless otherwise noted)
AVDD to AGND . . . . . . . . . . . . . . . . . . . . . . ­0.3 V to +7 V
DVDD to DGND . . . . . . . . . . . . . . . . . . . . . . ­0.3 V to +7 V
AVDD to DVDD . . . . . . . . . . . . . . . . . . . . . ­0.3 V to +0.3 V
AGND to DGND. . . . . . . . . . . . . . . . . . . . . . ­0.3 V to +0.3 V
Digital I/O Voltage to DGND . . . . . ­0.3 V to DVDD + 0.3 V
Analog I/O Voltage to AGND . . . . . ­0.3 V to AVDD + 0.3 V
Operating Temperature Range
Industrial (B Version) . . . . . . . . . . . . . . . . ­40
°
C to +85
°
C
Storage Temperature Range . . . . . . . . . . . . ­65
°
C to +150
°
C
Maximum Junction Temperature . . . . . . . . . . . . . . . .+150
°
C
TSSOP
JA
Thermal Impedance . . . . . . . . . . . . . . . 158
°
C/W
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . +215
°
C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . .+220
°
C
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . > 4500 V
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating condi-
tions for extended periods may affect device reliability.
ORDERING GUIDE
Temperature
Package
Package
Model
Range
Description
Option*
AD9835BRU
­40
°
C to +85
°
C
16-Lead TSSOP RU-16
*RU = Thin Shrink Small Outline Package (TSSOP).
PIN CONFIGURATION
14
13
12
11
16
15
10
9
8
1
2
3
4
7
6
5
TOP VIEW
(Not to Scale)
AD9835
FS ADJUST
AGND
IOUT
AVDD
COMP
REFIN
REFOUT
DVDD
FSELECT
PSEL1
PSEL0
DGND
MCLK
SCLK
SDATA
FSYNC
TERMINOLOGY
Integral Nonlinearity
This is the maximum deviation of any code from a straight line
passing through the endpoints of the transfer function. The end-
points of the transfer function are zero scale, a point 0.5 LSB
below the first code transition (000 . . . 00 to 000 . . . 01)
and full scale, a point 0.5 LSB above the last code transition
(111 . . . 10 to 111 . . . 11). The error is expressed in LSBs.
Differential Nonlinearity
This is the difference between the measured and ideal 1 LSB
change between two adjacent codes in the DAC.
Signal to (Noise + Distortion)
Signal to (Noise + Distortion) is measured signal to noise at the
output of the DAC. The signal is the rms magnitude of the
fundamental. Noise is the rms sum of all the nonfundamental
signals up to half the sampling frequency (f
MCLK
/2) but exclud-
ing the dc component. Signal to (Noise + Distortion) is depen-
dent on the number of quantization levels used in the digitization
process; the more levels, the smaller the quantization noise.
The theoretical Signal to (Noise + Distortion) ratio for a sine
wave input is given by
Signal to (Noise + Distortion) = (6.02N + 1.76) dB
where N is the number of bits. Thus, for an ideal 10-bit con-
verter, Signal to (Noise + Distortion) = 61.96 dB.
Total Harmonic Distortion
Total Harmonic Distortion (THD) is the ratio of the rms sum
of harmonics to the rms value of the fundamental. For the
AD9835, THD is defined as
THD
=
20 log
(V
2
2
+
V
3
2
+
V
4
2
+
V
5
2
+
V
6
2
)
V
1
where V
1
is the rms amplitude of the fundamental and V
2
, V
3
,
V
4
, V
5
and V
6
are the rms amplitudes of the second through the
sixth harmonic.
Output Compliance
The output compliance refers to the maximum voltage that can
be generated at the output of the DAC to meet the specifica-
tions. When voltages greater than that specified for the output
compliance are generated, the AD9835 may not meet the speci-
fications listed in the data sheet.
Spurious Free Dynamic Range
Along with the frequency of interest, harmonics of the funda-
mental frequency and images of the MCLK frequency are
present at the output of a DDS device. The spurious free dy-
namic range (SFDR) refers to the largest spur or harmonic
present in the band of interest. The wideband SFDR gives the
magnitude of the largest harmonic or spur relative to the magni-
tude of the fundamental frequency in the bandwidth
±
2 MHz
about the fundamental frequency. The narrow band SFDR gives
the attenuation of the largest spur or harmonic in a bandwidth of
±
50 kHz about the fundamental frequency.
Clock Feedthrough
There will be feedthrough from the MCLK input to the analog
output. Clock feedthrough refers to the magnitude of the
MCLK signal relative to the fundamental frequency in the
AD9835's output spectrum.
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AD9835
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PIN FUNCTION DESCRIPTIONS
Pin #
Mnemonic
Function
ANALOG SIGNAL AND REFERENCE
1
FS ADJUST
Full-Scale Adjust Control. A resistor (R
SET
) is connected between this pin and AGND. This determines
the magnitude of the full-scale DAC current. The relationship between R
SET
and the full-scale current is
as follows:
IOUT
FULL-SCALE
= 12.5
×
V
REFIN
/R
SET
V
REFIN
= 1.21 V nominal, R
SET
= 3.9 k
typical
2
REFIN
Voltage Reference Input. The AD9835 can be used with either the onboard reference, which is available
from pin REFOUT, or an external reference. The reference to be used is connected to the REFIN pin.
The AD9835 accepts a reference of 1.21 V nominal.
3
REFOUT
Voltage Reference Output. The AD9835 has an onboard reference of value 1.21 V nominal. The refer-
ence is made available on the REFOUT pin. This reference is used as the reference to the DAC by con-
necting REFOUT to REFIN. REFOUT should be decoupled with a 10 nF capacitor to AGND.
14
IOUT
Current Output. This is a high impedance current source. A load resistor should be connected between
IOUT and AGND.
16
COMP
Compensation pin. This is a compensation pin for the internal reference amplifier. A 10 nF decoupling
ceramic capacitor should be connected between COMP and AVDD.
POWER SUPPLY
4
DVDD
Positive Power Supply for the Digital Section. A 0.1
µ
F decoupling capacitor should be connected be-
tween DVDD and DGND. DVDD can have a value of +5 V
±
5%.
5
DGND
Digital Ground.
13
AGND
Analog Ground.
15
AVDD
Positive Power Supply for the Analog Section. A 0.1
µ
F decoupling capacitor should be connected be-
tween AVDD and AGND. AVDD can have a value of +5 V
±
5%.
DIGITAL INTERFACE AND CONTROL
6
MCLK
Digital Clock Input. DDS output frequencies are expressed as a binary fraction of the frequency of MCLK.
The output frequency accuracy and phase noise are determined by this clock.
7
SCLK
Serial Clock, Logic Input. Data is clocked into the AD9835 on each falling SCLK edge.
8
SDATA
Serial Data In, Logic Input. The 16-bit serial data word is applied to this input.
9
FSYNC
Data Synchronization Signal, Logic Input. When this input is taken low, the internal logic is informed
that a new word is being loaded into the device.
10
FSELECT
Frequency Select Input. FSELECT controls which frequency register, FREQ0 or FREQ1, is used in the
phase accumulator. The frequency register to be used can be selected using the pin FSELECT or the bit
FSELECT. FSELECT is sampled on the rising MCLK edge. FSELECT needs to be in steady state
when an MCLK rising edge occurs. If FSELECT changes value when a rising edge occurs, there is an
uncertainty of one MCLK cycle as to when control is transferred to the other frequency register. To avoid
any uncertainty, a change on FSELECT should not coincide with an MCLK rising edge. When the bit is
being used to select the frequency register, the pin FSELECT should be tied to DGND.
11, 12
PSEL0, PSEL1
Phase Select Input. The AD9835 has four phase registers. These registers can be used to alter the value
being input to the COS ROM. The contents of the phase register are added to the phase accumula-
tor output, the inputs PSEL0 and PSEL1 selecting the phase register to be used. Alternatively, the
phase register to be used can be selected using bits PSEL0 and PSEL1. Like the FSELECT input,
PSEL0 and PSEL1 are sampled on the rising MCLK edge. Therefore, these inputs need to be in
steady state when an MCLK rising edge occurs or there is an uncertainty of one MCLK cycle as to
when control is transferred to the selected phase register. When the phase registers are being con-
trolled by the bits PSEL0 and PSEL1, the pins should be tied to DGND.
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Table V. Commands
C3
C2
C1
C0
Command
0
0
0
0
Write 16 Phase bits (Present 8 Bits + 8 Bits
in Defer Register) to Selected PHASE
REG.
0
0
0
1
Write 8 Phase bits to Defer Register.
0
0
1
0
Write 16 Frequency bits (Present 8 Bits
+ 8 Bits in Defer Register) to Selected
FREQ REG.
0
0
1
1
Write 8 Frequency bits to Defer Register.
0
1
0
0
Bits D9 (PSEL0) and D10 (PSEL1) are
used to Select the PHASE REG when
SELSRC = 1. When SELSRC = 0, the
PHASE REG is selected using the pins
PSEL0 and PSEL1 Respectively.
0
1
0
1
Bit D11 is used to select the FREQ REG
when SELSRC = 1. When SELSRC = 0,
the FREQ REG is selected using the pin
FSELECT.
0
1
1
0
This command is used to control the
PSEL0, PSEL1 and FSELECT bits
using only one write. Bits D9 and D10
are used to select the PHASE REG and
Bit 11 is used to select the FREQ REG
when SELSRC = 1. When SELSRC = 0,
the PHASE REG is selected using the
pins PSEL0 and PSEL1 and the FREQ
REG is selected using the pin FSELECT.
0
1
1
1
Reserved. Configures the AD9835 for
Test Purposes.
Table VI. Controlling the AD9835
D15 D14 Command
1
0
Selects source of Control for the PHASE and
FREQ Registers and Enables Synchronization. Bit
D13 is the SYNC Bit. When this bit is High, read-
ing of the FSELECT, PSEL0 and PSEL1 bits/pins
and the loading of the Destination Register with
data is synchronized with the rising edge of MCLK.
The latency is increased by 2 MCLK cycles when
SYNC = 1. When SYNC = 0, the loading of the
data and the sampling of FSELECT/PSEL0/PSEL1
occurs asynchronously. Bit D12 is the Select
Source Bit (SELSRC). When this bit Equals 1, the
PHASE/FREQ REG is Selected using the bits
FSELECT, PSEL0 and PSEL1. When SELSRC =
0, the PHASE/FREQ REG is Selected using the
pins FSELECT, PSEL0 and PSEL1.
1
1
Sleep, Reset and Clear. D13 is the SLEEP bit. When
this bit equals 1, the AD9835 is powered down, inter-
nal clocks are disabled and the DAC's current sources
and REFOUT are turned off. When SLEEP = 0, the
AD9835 is powered up. When RESET (D12) = 1,
the phase accumulator is set to zero phase which
corresponds to an analog output of full scale. When
CLR (D11) = 1, SYNC and SELSRC are set to
zero. CLR automatically resets to zero.
Table I. Control Registers
Register
Size
Description
FREQ0 REG
32 Bits
Frequency Register 0. This de-
fines the output frequency, when
FSELECT = 0, as a fraction of the
MCLK frequency.
FREQ1 REG
32 Bits
Frequency Register 1. This de-
fines the output frequency, when
FSELECT = 1, as a fraction of the
MCLK frequency.
PHASE0 REG
12 Bits
Phase Offset Register 0. When
PSEL0 = PSEL1 = 0, the contents
of this register are added to the
output of the phase accumulator.
PHASE1 REG
12 Bits
Phase Offset Register 1. When
PSEL0 = 1 and PSEL1 = 0, the con-
tents of this register are added to the
output of the phase accumulator.
PHASE2 REG
12 Bits
Phase Offset Register 2. When
PSEL0 = 0 and PSEL1 = 1, the
contents of this register are added to
the output of the phase accumulator.
PHASE3 REG
12 Bits
Phase Offset Register 3. When
PSEL0 = PSEL1 = 1, the contents
of this register are added to the
output of the phase accumulator.
Table II. Addressing the Registers
A3
A2
A1
A0
Destination Register
0
0
0
0
FREG0 REG 8 L LSBs
0
0
0
1
FREG0 REG 8 H LSBs
0
0
1
0
FREG0 REG 8 L MSBs
0
0
1
1
FREG0 REG 8 H MSBs
0
1
0
0
FREG1 REG 8 L LSBs
0
1
0
1
FREG1 REG 8 H LSBs
0
1
1
0
FREG1 REG 8 L MSBs
0
1
1
1
FREG1 REG 8 H MSBs
1
0
0
0
PHASE0 REG 8 LSBs
1
0
0
1
PHASE0 REG 8 MSBs
1
0
1
0
PHASE1 REG 8 LSBs
1
0
1
1
PHASE1 REG 8 MSBs
1
1
0
0
PHASE2 REG 8 LSBs
1
1
0
1
PHASE2 REG 8 MSBs
1
1
1
0
PHASE3 REG 8 LSBs
1
1
1
1
PHASE3 REG 8 MSBs
Table III. 32-Bit Frequency Word
s
B
S
M
6
1
s
B
S
L
6
1
s
B
S
M
H
8
s
B
S
M
L
8
s
B
S
L
H
8
s
B
S
L
L
8
Table IV. 12-Bit Frequency Word
e
h
t
f
o
s
B
S
M
4
e
h
T
(
s
B
S
M
4
)
0
=
d
e
d
a
o
L
d
r
o
W
t
i
B
-
8
s
B
S
L
8
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AD9835
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Table VII. Writing to the AD9835 Data Registers
5
1
D
4
1
D
3
1
D
2
1
D
1
1
D
0
1
D
9
D
8
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
D
3
C
2
C
1
C
0
C
3
A
2
A
1
A
0
A
B
S
M
B
S
L
Table VIII. Setting SYNC and SELSRC
5
1
D
4
1
D
3
1
D
2
1
D
1
1
D
0
1
D
9
D
8
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
D
1
0
C
N
Y
S
C
R
S
L
E
S
X
X
X
X
X
X
X
X
X
X
X
X
Table IX. Power-Down, Resetting and Clearing the AD9835
5
1
D
4
1
D
3
1
D
2
1
D
1
1
D
0
1
D
9
D
8
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
D
1
1
P
E
E
L
S
T
E
S
E
R
R
L
C
X
X
X
X
X
X
X
X
X
X
X
Typical Performance Characteristics
OUTPUT FREQUENCY ­ MHz
0
­12
0
16
2
SIGNAL ATTENUATION ­ dB
4
6
8
10
12
14
­2
­4
­6
­8
­10
C
L
= 82pF
C
L
= 100pF
C
L
= 150pF
AVDD = DVDD = +5V
Figure 5. Signal Attenuation vs. Output Frequency for
Various Capacitive Load (R
L
= 300
)
MCLK FREQUENCY ­ MHz
30
25
20
15
10
0
10
50
20
TOTAL CURRENT ­ mA
30
40
5
T
A
= +25 C
AVDD = DVDD = +5V
Figure 6. Typical Current Consumption vs. MCLK Frequency
MCLK FREQUENCY ­ MHz
­64
­66
­68
­70
­72
­76
­74
10
50
20
SFDR (
50kHz) ­ dB
30
40
f
OUT
/f
MCLK
= 1/3
AVDD = DVDD = +5V
Figure 7. Narrow Band SFDR vs. MCLK Frequency
MCLK FREQUENCY ­ MHz
0
­10
­20
­30
­40
­60
­50
10
50
20
SFDR (
2MHz) ­ dB
30
40
f
OUT
/f
MCLK
= 1/3
AVDD = DVDD = +5V
Figure 8. Wide Band SFDR vs. MCLK Frequency
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AD9835
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f
OUT
/f
MCLK
­20
­30
­40
­50
­60
­80
­70
0.044
0.364
0.124
0.204
0.284
SFDR (
2MHz) ­ dB
0.084
0.164
0.244
0.324
AVDD = DVDD = +5V
50MHz
30MHz
10MHz
Figure 9. Wide Band SFDR vs. f
OUT
/f
MCLK
for Various MCLK
Frequencies
MCLK FREQUENCY ­ MHz
56
55
54
53
52
50
10
50
20
SNR ­ dB
30
40
51
f
OUT
/f
MCLK
= 1/3
AVDD = DVDD = +5V
Figure 10. SNR vs. MCLK Frequency
f
OUT
/f
MCLK
70
60
50
40
30
10
20
0.044
0.364
0.124
0.204
0.284
SNR ­ dB
0.084
0.164
0.244
0.324
AVDD = DVDD = +5V
50MHz
30MHz
10MHz
Figure 11. SNR vs. f
OUT
/f
MCLK
for Various MCLK
Frequencies
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 12. f
MCLK
= 50 MHz, f
OUT
= 2.1 MHz. Frequency
Word = ACO8312
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 13. f
MCLK
= 50 MHz, f
OUT
= 3.1 MHz. Frequency
Word = FDF3B64
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 14. f
MCLK
= 50 MHz, f
OUT
= 7.1 MHz. Frequency
Word = 245AICAC
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AD9835
­9­
REV. 0
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 15. f
MCLK
= 50 MHz, f
OUT
= 9.1 MHz. Frequency
Word = 2E978D50
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 16. f
MCLK
= 50 MHz, f
OUT
= 11.1 MHz. Frequency
Word = 38D4FDF4
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 17. f
MCLK
= 50 MHz, f
OUT
= 13.1 MHz. Frequency
Word = 43126E98
RBW 1kHz VBW 3kHz ST 50 SEC
10dB/DIV
0Hz
START
25MHz
STOP
Figure 18. f
MCLK
= 50 MHz, f
OUT
= 16.5 MHz. Frequency
Word = 547AE148
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AD9835
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CIRCUIT DESCRIPTION
The AD9835 provides an exciting new level of integration for
the RF/Communications system designer. The AD9835 com-
bines the Numerical Controlled Oscillator (NCO), COS Look-Up
Table, Frequency and Phase Modulators, and a Digital-to-
Analog Converter on a single integrated circuit.
The internal circuitry of the AD9835 consists of three main
sections. These are:
Numerical Controlled Oscillator (NCO) + Phase Modulator
COS Look-Up Table
Digital-to-Analog Converter
The AD9835 is a fully integrated Direct Digital Synthesis (DDS)
chip. The chip requires one reference clock, one low precision
resistor and eight decoupling capacitors to provide digitally
created sine waves up to 25 MHz. In addition to the generation
of this RF signal, the chip is fully capable of a broad range of
simple and complex modulation schemes. These modulation
schemes are fully implemented in the digital domain allowing
accurate and simple realization of complex modulation algo-
rithms using DSP techniques.
THEORY OF OPERATION
Cos waves are typically thought of in terms of their magnitude
form a(t) = cos (
t). However, these are nonlinear and not easy
to generate except through piece-wise construction. On the
other hand, the angular information is linear in nature. That is,
the phase angle rotates through a fixed angle for each unit of
time. The angular rate depends on the frequency of the signal
by the traditional rate of
= 2
f.
MAGNITUDE
PHASE
+1
0
­1
2
0
Figure 19. Cos Wave
Knowing that the phase of a cos wave is linear and given a refer-
ence interval (clock period), the phase rotation for that period
can be determined.
Phase =
t
Solving for
=
Phase/
t = 2
f
Solving for f and substituting the reference clock frequency for
the reference period (1/f
MCLK
=
t)
f =
Phase
×
f
MCLK
/2
The AD9835 builds the output based on this simple equation.
A simple DDS chip can implement this equation with three
major subcircuits.
Numerical Controlled Oscillator and Phase Modulator
This consists of two frequency select registers, a phase accumu-
lator and four phase offset registers. The main component of the
NCO is a 32-bit phase accumulator which assembles the phase
component of the output signal. Continuous time signals have a
phase range of 0
to 2
. Outside this range of numbers, the
sinusoid functions repeat themselves in a periodic manner. The
digital implementation is no different. The accumulator simply
scales the range of phase numbers into a multibit digital word.
The phase accumulator in the AD9835 is implemented with
32 bits. Therefore, in the AD9835, 2
= 2
32
. Likewise, the
Phase term is scaled into this range of numbers 0 <
Phase
< 2
32
­ 1. Making these substitutions into the equation above
f =
Phase
×
f
MCLK
/2
32
where 0 <
Phase < 2
32
The input to the phase accumulator (i.e., the phase step) can be
selected either from the FREQ0 Register or FREQ1 Register
and this is controlled by the FSELECT pin or the FSELECT
bit. NCOs inherently generate continuous phase signals, thus
avoiding any output discontinuity when switching between
frequencies.
Following the NCO, a phase offset can be added to perform
phase modulation using the 12-bit PHASE Registers. The con-
tents of this register are added to the most significant bits of the
NCO. The AD9835 has four PHASE registers, the resolution
of these registers being 2
/4096.
COS Look-Up Table (LUT)
To make the output useful, the signal must be converted from
phase information into a sinusoidal value. Since phase informa-
tion maps directly into amplitude, a ROM LUT converts the
phase information into amplitude. To do this, the digital phase
information is used to address a COS ROM LUT. Although
the NCO contains a 32-bit phase accumulator, the output of the
NCO is truncated to 12 bits. Using the full resolution of the
phase accumulator is impractical and unnecessary as this would
require a look-up table of 2
32
entries.
It is necessary only to have sufficient phase resolution in the
LUTs such that the dc error of the output waveform is domi-
nated by the quantization error in the DAC. This requires the
look-up table to have two more bits of phase resolution than the
10-bit DAC.
Digital-to-Analog Converter
The AD9835 includes a high impedance current source 10-bit
DAC, capable of driving a wide range of loads at different
speeds. Full-scale output current can be adjusted, for optimum
power and external load requirements, through the use of a
single external resistor (R
SET
).
The DAC is configured for single-ended operation. The load
resistor can be any value required, as long as the full-scale volt-
age developed across it does not exceed the voltage compliance
range. Since full-scale current is controlled by R
SET
, adjust-
ments to R
SET
can balance changes made to the load resistor.
However, if the DAC full-scale output current is significantly
less than 4 mA, the DAC's linearity may degrade.
DSP and MPU Interfacing
The AD9835 has a serial interface, with 16 bits being loaded
during each write cycle. SCLK, SDATA and FSYNC are used
to load the word into the AD9835. When FSYNC is taken low,
the AD9835 is informed that a word is being written to the
device. The first bit is read into the device on the next SCLK
falling edge with the remaining bits being read into the device
on the subsequent SCLK falling edges. FSYNC frames the
16 bits; therefore, when 16 SCLK falling edges have occurred,
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AD9835
­11­
REV. 0
FSYNC should be taken high again. The SCLK can be con-
tinuous or, alternatively, the SCLK can idle high or low be-
tween write operations.
When writing to a frequency/phase register, the first four bits
identify whether a frequency or phase register is being written
to, the next four bits contain the address of the destination
register while the 8 LSBs contain the data. Table II lists the
addresses for the phase/frequency registers while Table III lists
the commands.
Within the AD9835, 16-bit transfers are used when loading the
destination frequency/phase register. There are two modes for
loading a register--direct data transfer and a deferred data
transfer. With a deferred data transfer, the 8-bit word is loaded
into the defer register (8 LSBs or 8 MSBs). However, this data
is not loaded into the 16-bit data register so the destination
register is not updated. With a direct data transfer, the 8-bit
word is loaded into the appropriate defer register (8 LSBs or
8 MSBs). Immediately following the loading of the defer regis-
ter, the contents of the complete defer register are loaded into
the 16-bit data register and the destination register is loaded on
the next MCLK rising edge. When a destination register is
addressed, a deferred transfer is needed first, followed by a
direct transfer. When all 16 bits of the defer register contain
relevant data, the destination register can then be updated using
8-bit loading rather than 16-bit loading, i.e., direct data trans-
fers can be used. For example, after a new 16-bit word has
been loaded to a destination register, the defer register will also
contain this word. If the next write instruction is to the same
destination register, the user can use direct data transfers
immediately.
When writing to a phase register, the 4 MSBs of the 16-bit word
loaded into the data register should be zero (the phase registers
are 12 bits wide).
To alter the entire contents of a frequency register, four write
operations are needed. However, the 16 MSBs of a frequency
word are contained in a separate register to the 16 LSBs. There-
fore, the 16 MSBs of the frequency word can be altered inde-
pendent of the 16 LSBs.
The phase and frequency registers to be used are selected using
the pins FSELECT, PSEL0 and PSEL1 or the corresponding
bits can be used. Bit SELSRC determines whether the bits or
the pins are used. When SELSRC = 0, the pins are used while
the bits are used when SELSRC = 1. When CLR is taken high,
SELSRC is set to 0 so that the pins are the default source.
Data transfers from the serial (defer) register to the 16-bit data
register, and the FSELECT and PSEL registers, occur following
the 16th falling SCLK edge. Transfer of the data from the 16-bit
data register to the destination register or from the FSELECT/
PSEL register to the respective multiplexer occurs on the next
MCLK rising edge. Since the SCLK and the MCLK are asyn-
chronous, an MCLK rising edge may occur while the data bits
are in transitional state, which will cause a brief spurious DAC
output if the register being written to is generating the DAC
output. To avoid such spurious outputs, the AD9835 contains
synchronizing circuitry. When the SYNC bit is set to 1, the
synchronizer is enabled and data transfers from the serial
register (defer register) to the 16-bit data register and the
FSELECT/PSEL registers occur following a two-stage pipeline
delay which is triggered on the MCLK falling edge. The pipe-
line delay ensures that the data is valid when the transfer occurs.
Similarly, selection of the frequency/phase registers using the
FSELECT/PSEL pins is synchronized with the MCLK rising
edge when SYNC = 1. When SYNC = 0, the synchronizer is
bypassed.
Selecting the frequency/phase registers using the pins is
synchronized with MCLK internally also when SYNC = 1 to
ensure that these inputs are valid at the MCLK rising edge. If
times t
11
and t
11A
are met, the inputs will be at steady state at
the MCLK rising edge. However, if times t
11
and t
11A
are
violated, the internal synchronizing circuitry will delay the
instant at which the pins are sampled, ensuring that the inputs
are valid at the sampling instant.
A latency is associated with each operation. When inputs
FSELECT/PSEL change value, there will be a pipeline delay
before control is transferred to the selected register--there will
be a pipeline delay before the analog output is controlled by
the selected register. When times t
11
and t
11A
are met, PSEL0,
PSEL1 and FSELECT have latencies of six MCLK cycles when
SYNC = 0. When SYNC = 1, the latency is increased to
8 MCLK cycles. When times t
11
and t
11A
are not met, the
latency can increase by one MCLK cycle. Similarly, there is a
latency associated with each write operation. If a selected
frequency/phase register is loaded with a new word, there is a
delay of 6 to 7 MCLK cycles before the analog output will
change (there is an uncertainty of one MCLK cycle regarding
the MCLK rising edge at which the data is loaded into the
destination register). When SYNC = 1, the latency will be 8 or
9 MCLK cycles.
The flowchart in Figure 20 shows the operating routine for the
AD9835. When the AD9835 is powered up, the part should be
reset. This will reset the phase accumulator to zero so that the
analog output is at full scale. To avoid spurious DAC outputs
while the AD9835 is being initialized, the RESET bit should be
set to 1 until the part is ready to begin generating an output.
Taking CLR high will set SYNC and SELSRC to 0 so that the
FSELECT/PSEL pins are used to select the frequency/phase
registers and the synchronization circuitry is bypassed. A write
operation is needed to the SYNC/SELSRC register to enable
the synchronization circuitry or to change control to the
FSELECT/PSEL bits. RESET does not reset the phase and
frequency registers. These registers will contain invalid data
and should therefore be set to a known value by the user. The
RESET bit is then set to 0 to begin generating an output. A
signal will appear at the DAC output 6 MCLK cycles after
RESET is set to 0.
The analog output is f
MCLK
/2
32
×
FREG where FREG is the
value loaded into the selected frequency register. This signal
will be phase shifted by the amount specified in the selected
phase register (2
/4096
×
PHASEREG where PHASEREG is
the value contained in the selected phase register).
Control of the frequency/phase registers can be interchanged
from the pins to the bits.
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AD9835
­12­
REV. 0
DATA WRITE**
FREG<0> = f
OUT0
/f
MCLK
*2
32
FREG<1> = f
OUT1
/f
MCLK
*2
32
PHASEREG <3:0> = DELTA PHASE<0, 1, 2, 3>
SELECT DATA SOURCES***
SET FSELECT
SET PSEL0, PSEL1
INITIALIZATION*
WAIT 6 MCLK CYCLES (8 MCLK CYCLES IF SYNC = 1)
DAC OUTPUT
V
OUT
= V
REFIN
*6.25*R
OUT
/R
SET
*(1 + COS(2 (FREG*f
MCLK
*t/2
32
+ PHASEREG/2
12
)))
NO
CHANGE f
OUT
?
YES
NO
YES
CHANGE FREG?
NO
YES
CHANGE FSELECT
CHANGE PHASEREG?
NO
YES
CHANGE PSEL0, PSEL1
CHANGE PHASE?
Figure 20. Flowchart for AD9835 Initialization and Operation
INITIALIZATION*
CONTROL REGISTER WRITE
SET SLEEP
RESET = 1
CLR = 1
SET SYNC AND/OR SELSRC TO 1
YES
NO
CONTROL REGISTER WRITE
SYNC = 1
AND/OR
SELSRC = 1
WRITE INITIAL DATA
FREG<0> = f
OUT0
/f
MCLK
*2
32
FREG<1> = f
OUT1
/f
MCLK
*2
32
PHASEREG<3:0> = DELTA PHASE<0, 1, 2, 3>
SET PINS OR FREQUENCY/PHASE REGISTER WRITE
SET FSELECT, PSEL0 AND PSEL1
CONTROL REGISTER WRITE
SLEEP = 0
RESET = 0
CLR = 0
Figure 21. Initialization
DATA WRITE**
DEFERRED TRANSFER WRITE
WRITE 8 BITS TO DEFER REGISTER
DIRECT TRANSFER WRITE
WRITE PRESENT 8 BITS AND 8 BITS IN
DEFER REGISTER TO DATA REGISTER
WRITE ANOTHER WORD TO THIS
REGISTER?
WRITE A WORD TO ANOTHER REGISTER
CHANGE 8 BITS ONLY
YES
CHANGE 16 BITS
NO
YES
NO
Figure 22. Data Writes
SELECT DATA SOURCES***
FSELECT/PSEL PINS BEING USED?
YES
SELSRC = 0
SET PINS
SET FSELECT
SET PSEL0
SET PSEL1
FREQUENCY/PHASE REGISTER WRITE
SET FSELECT
SET PSEL0
SET PSEL1
SELSRC = 1
NO
Figure 23. Selecting Data Sources
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AD9835
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APPLICATIONS
The AD9835 contains functions that make it suitable for
modulation applications. The part can be used to perform
simple modulation such as FSK. More complex modulation
schemes such as GMSK and QPSK can also be implemented
using the AD9835. In an FSK application, the two frequency
registers of the AD9835 are loaded with different values; one
frequency will represent the space frequency while the other will
represent the mark frequency. The digital data stream is fed to
the FSELECT pin, which will cause the AD9835 to modulate
the carrier frequency between the two values.
The AD9835 has four phase registers; this enables the part to
perform PSK. With phase shift keying, the carrier frequency is
phase shifted, the phase being altered by an amount that is
related to the bit stream being input to the modulator. The
presence of four shift registers eases the interaction needed
between the DSP and the AD9835.
The AD9835 is also suitable for signal generator applications.
With its low current consumption, the part is suitable for
applications in which it can be used as a local oscillator.
Grounding and Layout
The printed circuit board that houses the AD9835 should be
designed so that the analog and digital sections are separated
and confined to certain areas of the board. This facilitates the
use of ground planes which can be separated easily. A minimum
etch technique is generally best for ground planes as it gives the
best shielding. Digital and analog ground planes should only be
joined in one place. If the AD9835 is the only device requiring
an AGND to DGND connection, then the ground planes
should be connected at the AGND and DGND pins of the
AD9835. If the AD9835 is in a system where multiple devices
require AGND to DGND connections, the connection should
be made at one point only, a star ground point that should be
established as close as possible to the AD9835.
Avoid running digital lines under the device as these will couple
noise onto the die. The analog ground plane should be allowed
to run under the AD9835 to avoid noise coupling. The power
supply lines to the AD9835 should use as large a track as is
possible to provide low impedance paths and reduce the effects
of glitches on the power supply line. Fast switching signals
such as clocks should be shielded with digital ground to avoid
radiating noise to other sections of the board. Avoid crossover
of digital and analog signals. Traces on opposite sides of the
board should run at right angles to each other. This will reduce
the effects of feedthrough through the board. A microstrip
technique is by far the best but is not always possible with a
double-sided board. In this technique, the component side of
the board is dedicated to ground planes while signals are placed
on the other side.
Good decoupling is important. The analog and digital supplies
to the AD9835 are independent and separately pinned out to
minimize coupling between analog and digital sections of the
device. All analog and digital supplies should be decoupled to
AGND and DGND respectively with 0.1
µ
F ceramic capacitors
in parallel with 10
µ
F tantalum capacitors. To achieve the best
from the decoupling capacitors, they should be placed as close
as possible to the device, ideally right up against the device. In
systems where a common supply is used to drive both the
AVDD and DVDD of the AD9835, it is recommended that the
system's AVDD supply be used. This supply should have the
recommended analog supply decoupling between the AVDD
pins of the AD9835 and AGND and the recommended digital
supply decoupling capacitors between the DVDD pins and
DGND.
Interfacing the AD9835 to Microprocessors
The AD9835 has a standard serial interface that allows the part
to interface directly with several microprocessors. The device
uses an external serial clock to write the data/control informa-
tion into the device. The serial clock can have a frequency of
20 MHz maximum. The serial clock can be continuous or it
can idle high or low between write operations. When data/
control information is being written to the AD9835, FSYNC
is taken low and held low while the 16 bits of data are being
written into the AD9835. The FSYNC signal frames the 16 bits
of information being loaded into the AD9835.
AD9835-to-ADSP-21xx Interface
Figure 24 shows the serial interface between the AD9835 and
the ADSP-21xx. The ADSP-21xx should be set up to operate
in the SPORT Transmit Alternate Framing Mode (TFSW = 1).
The ADSP-21xx is programmed through the SPORT control
register and should be configured as follows: Internal clock
operation (ISCLK = 1), Active low framing (INVTFS = 1),
16-bit word length (SLEN = 15), Internal frame sync signal
(ITFS = 1), Generate a frame sync for each write operation
(TFSR = 1). Transmission is initiated by writing a word to the
Tx register after the SPORT has been enabled. The data is
clocked out on each rising edge of the serial clock and clocked
into the AD9835 on the SCLK falling edge.
ADSP-2101/
ADSP-2103
AD9835
TFS
DT
SCLK
FSYNC
ADDITIONAL PINS OMITTED FOR CLARITY
SDATA
SCLK
Figure 24. ADSP-2101/ADSP-2103-to-AD9835 Interface
AD9835-to-68HC11/68L11 Interface
Figure 25 shows the serial interface between the AD9835 and
the 68HC11/68L11 microcontroller. The microcontroller is
configured as the master by setting bit MSTR in the SPCR to 1
and, this provides a serial clock on SCK while the MOSI output
drives the serial data line SDATA. Since the microcontroller
does not have a dedicated frame sync pin, the FSYNC signal is
derived from a port line (PC7). The setup conditions for cor-
rect operation of the interface are as follows: the SCK idles high
between write operations (CPOL = 0), data is valid on the SCK
falling edge (CPHA = 1). When data is being transmitted to the
AD9835, the FSYNC line is taken low (PC7). Serial data from
the 68HC11/68L11 is transmitted in 8-bit bytes with only eight
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AD9835
­14­
REV. 0
falling clock edges occurring in the transmit cycle. Data is
transmitted MSB first. In order to load data into the AD9835,
PC7 is held low after the first eight bits are transferred and a
second serial write operation is performed to the AD9835. Only
after the second eight bits have been transferred should FSYNC
be taken high again.
68HC11/68L11
AD9835
PC7
MOSI
SCK
SDATA
SCLK
FSYNC
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 25. 68HC11/68L11-to-AD9835 Interface
AD9835-to-80C51/80L51 Interface
Figure 26 shows the serial interface between the AD9835 and
the 80C51/80L51 microcontroller. The microcontroller is oper-
ated in Mode 0 so that TXD of the 80C51/80L51 drives SCLK
of the AD9835 while RXD drives the serial data line SDATA.
The FSYNC signal is again derived from a bit programmable
pin on the port (P3.3 being used in the diagram). When data is
to be transmitted to the AD9835, P3.3 is taken low. The
80C51/80L51 transmits data in 8-bit bytes thus, only eight
falling SCLK edges occur in each cycle. To load the remaining
eight bits to the AD9835, P3.3 is held low after the first eight
bits have been transmitted and a second write operation is initi-
ated to transmit the second byte of data. P3.3 is taken high
following the completion of the second write operation. SCLK
should idle high between the two write operations. The 80C51/
80L51 outputs the serial data in a format which has the LSB
first. The AD9835 accepts the MSB first (the 4 MSBs being the
control information, the next 4 bits being the address while the
8 LSBs contain the data when writing to a destination register).
Therefore, the transmit routine of the 80C51/80L51 must take
this into account and rearrange the bits so that the MSB is out-
put first.
80C51/80L51
AD9835
P3.3
RXD
TXD
SDATA
SCLK
FSYNC
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 26. 80C51/80L51 to AD9835 Interface
AD9835-to-DSP56002 Interface
Figure 27 shows the interface between the AD9835 and the
DSP56002. The DSP56002 is configured for normal mode
asynchronous operation with a Gated internal clock (SYN = 0,
GCK = 1, SCKD = 1). The frame sync pin is generated inter-
nally (SC2 = 1), the transfers are 16 bits wide (WL1 = 1, WL0
= 0) and the frame sync signal will frame the 16 bits (FSL = 0).
The frame sync signal is available on pin SC2 but, it needs to be
inverted before being applied to the AD9835. The interface to
the DSP56000/DSP56001 is similar to that of the DSP56002.
DSP56002
AD9835
SC2
STD
SCK
SDATA
SCLK
FSYNC
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 27. AD9835-to-DSP56002 Interface
AD9835 Evaluation Board
The AD9835 Evaluation Board allows designers to evaluate the
high performance AD9835 DDS Modulator with a minimum of
effort.
To prove that this device will meet the user's waveform synthe-
sis requirements, the user only requires a 5 V power supply, an
IBM-compatible PC and a spectrum analyzer along with the
evaluation board. The evaluation setup is shown below.
The DDS Evaluation kit includes a populated, tested AD9835
printed circuit board along with the software that controls the
AD9835 in a Windows
®
environment.
AD9835.EXE
IBM-COMPATIBLE PC
PARALLEL PORT
CENTRONICS
PRINTER CABLE
AD9835 EVALUATION
BOARD
Figure 28. AD9835 Evaluation Board Setup
Using the AD9835 Evaluation Board
The AD9835 Evaluation kit is a test system designed to simplify
the evaluation of the AD9835. Provisions to control the AD9835
from the printer port of an IBM-compatible PC are included
along with the necessary software. An application note is also
available with the evaluation board which gives information on
operating the evaluation board.
Prototyping Area
An area is available on the evaluation board where the user can
add additional circuits to the evaluation test set. Users may
want to build custom analog filters for the output or add buffers
and operational amplifiers to be used in the final application.
XO vs. External Clock
The AD9835 can operate with master clocks up to 50 MHz. A
50 MHz oscillator is included on the evaluation board. How-
ever, this oscillator can be removed and an external CMOS
clock connected to the part, if required.
Power Supply
Power to the AD9835 Evaluation Board must be provided ex-
ternally through the pin connections. The power leads should be
twisted to reduce ground loops.
Windows is a registered trademark of Microsoft Corporation.
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AD9835
­15­
REV. 0
C1
0.1 F
DVDD
AVDD
C2
0.1 F
4
15
DVDD
AVDD
16
2
3
1
14
COMP
REFIN
REFOUT
FSADJUST
IOUT
AVDD
C3
10nF
REFIN
C4
10nF
LK4
R5
3.9k
IOUT
C8
10 F
C7
0.1 F
DVDD
J2
J3
C9
0.1 F
C10
10 F
AVDD
R6
300
DGND
AGND
5
13
11
12
10
6
9
8
7
MCLK
FSELECT
PSEL0
PSEL1
FSYNC
SDATA
SCLK
16
14
9
20
11
6
4
DVDD
C6
0.1 F
1 10 19
U2
J1
SCLK
SDATA
FSYNC
R3
10k
R1
10k
R2
10k
PSEL1
PSEL0
FSELECT
LK1
LK2
LK3
SW
DVDD
MCLK
R4
50
DGND
DVDD
OUT
DVDD
C5
0.1 F
U3
SCLK
SDATA
FSYNC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
U1
AD9835
XTAL1
Figure 29. Evaluation Board Layout
Integrated Circuits
XTAL1
OSC XTAL 50 MHz
U1
AD9835 (16-Lead TSSOP)
U2
74HCT244 Buffer
Capacitors
C1, C2
0.1
µ
F Ceramic Chip Capacitor
C3, C4
10 nF Ceramic Capacitor
C5, C6, C7, C9
0.1
µ
F Ceramic Capacitor
C8, C10
10
µ
F Tantalum Capacitor
Resistors
R1­R3
10 k
Resistor
R4
50
Resistor
R5
3.9 k
Resistor
R6
300
Resistor
Links
LK1­LK3
Three Pin Link
LK4
Two Pin Link
Switch
SW
End Stackable Switch (SDC Double
Throw)
Sockets
MCLK, PSEL0,
Subminiature BNC Connector
PSEL1, FSELECT,
IOUT, REFIN
Connectors
J1
36-Pin Edge Connector
J2, J3
PCB Mounting Terminal Block
background image
AD9835
­16­
REV. 0
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
C3309­8­7/98
PRINTED IN U.S.A.
16-Lead Thin Shrink Small Outline Package (TSSOP)
(RU-16)
16
9
8
1
0.201 (5.10)
0.193 (4.90)
0.256 (6.50)
0.246 (6.25)
0.177 (4.50)
0.169 (4.30)
PIN 1
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.0118 (0.30)
0.0075 (0.19)
0.0256
(0.65)
BSC
0.0433
(1.10)
MAX
0.0079 (0.20)
0.0035 (0.090)
0.028 (0.70)
0.020 (0.50)