1
LTC1655/LTC1655L
16-Bit Rail-to-Rail
Micropower DACs in
SO-8 Package
s
16-Bit Monotonicity Over Temperature
s
Deglitched Rail-to-Rail Voltage Output
s
SO-8 Package
s
I
CC(TYP)
: 600
µ
A
s
Internal Reference: 2.048V (LTC1655)
1.25V (LTC1655L)
s
Maximum DNL Error:
±
1LSB
s
Settling Time: 20
µ
S to
±
1LSB
s
750kHz Max Update Rate
s
Power-On Reset to Zero Volts
s
3-Wire Cascadable Serial Interface
s
Low Cost
s
Pin Compatible Upgrade for LTC1451 12-Bit DAC
Family
The LTC
®
1655/LTC1655L are rail-to-rail voltage output,
16-bit digital-to-analog converters in an SO-8 package.
They include an output buffer and a reference. The 3-wire
serial interface is compatible with SPI/QSPI and
MICROWIRE
TM
protocols. The CLK input has a Schmitt
trigger that allows direct optocoupler interface.
The LTC1655 has an onboard 2.048V reference that can be
overdriven to a higher voltage. The output swings from 0V
to 4.096V when using the internal reference. The typical
power dissipation is 3.0mW on a single 5V supply.
The LTC1655L has an onboard 1.25V reference that can be
overdriven to a higher voltage. The output swings from 0V
to 2.5V when using the internal reference. The typical
power dissipation is 1.8mW on a single 3V supply.
The LTC1655/LTC1655L are pin compatible with Linear
Technology's 12-bit V
OUT
DAC family, allowing an easy
upgrade path. They are the only buffered 16-bit DACs in
an SO-8 package and they include an onboard reference
for standalone performance.
s
Digital Calibration
s
Industrial Process Control
s
Automatic Test Equipment
s
Cellular Telephones
, LTC and LT are registered trademarks of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
+
16-BIT
DAC
LTC1655: 4.5V TO 5.5V
LTC1655L: 2.7V TO 5.5V
LTC1655: 2.048V
LTC1655L: 1.25V
GND
POWER-ON
RESET
TO
OTHER
DACS
16-BIT
SHIFT
REG
AND
DAC
LATCH
µ
P
D
IN
V
CC
16
REF
2
8
6
D
OUT
4
5
1655/55L TA01
CLK
1
CS/LD
3
7
V
OUT
REF
Functional Block Diagram: 16-Bit Rail-to-Rail DAC
Differential Nonlinearity
vs Input Code
CODE
0
1.0
0.2
0.4
0.6
0.8
0
0.2
0.4
0.6
0.8
1.0
DNL ERROR (LSB)
16384
32768
1655/55L TA02
49152
65535
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
FU CTIO AL BLOCK DIAGRA
U
U
W
2
LTC1655/LTC1655L
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
ORDER PART
NUMBER
W
U
U
PACKAGE/ORDER I FOR ATIO
LTC1655CN8
LTC1655IN8
LTC1655CS8
LTC1655IS8
LTC1655LCN8
LTC1655LIN8
LTC1655LCS8
LTC1655LIS8
S8 PART MARKING
1655
1655I
1655L
1655LI
Consult factory for Military grade parts.
(Note 1)
V
CC
to GND .............................................. 0.5V to 7.5V
TTL Input Voltage .................................... 0.5V to 7.5V
V
OUT
, REF
....................................... 0.5V to V
CC
+ 0.5V
Maximum Junction Temperature ......................... 125
°
C
Operating Temperature Range
LTC1655C/LTC1655LC ........................... 0
°
C to 70
°
C
LTC1655I/LTC1655LI ........................ 40
°
C to 85
°
C
Storage Temperature Range ................ 65
°
C to 150
°
C
Lead Temperature (Soldering, 10 sec)................. 300
°
C
1
2
3
4
8
7
6
5
TOP VIEW
V
CC
V
OUT
REF
GND
CLK
D
IN
CS/LD
D
OUT
S8 PACKAGE
8-LEAD PLASTIC SO
N8 PACKAGE
8-LEAD PDIP
T
JMAX
= 125
°
C,
JA
= 100
°
C/W (N8)
T
JMAX
= 125
°
C,
JA
= 150
°
C/W (S8)
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25
°
C.
V
CC
= 4.5V to 5.5V (LTC1655), V
CC
= 2.7V to 5.5V (LTC1655L); V
OUT
unloaded, REF unloaded, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DAC
Resolution
q
16
Bits
Monotonicity
q
16
Bits
DNL
Differential Nonlinearity
Guaranteed Monotonic (Note 2)
LTC1655, REF = 2.2V, V
CC
= 5V (Note 8) (External)
q
±
0.3
±
1.0
LSB
LTC1655L, REF = 2.2V, V
CC
= 5V (Note 8) (External)
q
±
0.5
±
1.0
LSB
INL
Integral Nonlinearity
LTC1655, REF = 2.2V, V
CC
= 5V (Note 8) (External)
q
±
8
±
20
LSB
LTC1655L, REF = 2.2V, V
CC
= 5V (Note 8) (External)
q
±
8
±
20
LSB
ZSE
Zero Scale Error
LTC1655
q
0
3.0
mV
LTC1655L
q
0
3.5
mV
V
OS
Offset Error
Measured at Code 200
LTC1655, REF = 2.2V, V
CC
= 5V (Note 8) (External)
q
±
0.5
±
3.0
mV
LTC1655L, REF = 1.3V, V
CC
= 2.7V (Note 8) (External)
q
±
0.5
±
3.5
mV
V
OS
TC
Offset Error Tempco
±
5
µ
V/
°
C
Gain Error
REF = 2.2V (External), V
CC
= 5V (Note 8)
q
±
5
±
16
LSB
Gain Error Drift
0.5
ppm/
°
C
Power Supply
V
CC
Positive Supply Voltage
For Specified Performance
LTC1655
q
4.5
5.5
V
LTC1655L
q
2.7
5.5
V
I
CC
Supply Current
(Note 3)
q
600
1200
µ
A
3
LTC1655/LTC1655L
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25
°
C.
V
CC
= 4.5V to 5.5V (LTC1655), V
CC
= 2.7V to 5.5V (LTC1655L); V
OUT
unloaded, REF unloaded, unless otherwise noted.
Op Amp DC Performance
Short-Circuit Current Low
V
OUT
Shorted to GND
LTC1655
q
70
120
mA
LTC1655L
q
70
140
mA
Short-Circuit Current High
V
OUT
Shorted to V
CC
LTC1655
q
80
140
mA
LTC1655L
q
70
150
mA
Output Impedance to GND
Input Code = 0
LTC1655
q
40
120
LTC1655L
q
70
160
Output Line Regulation
Input Code = 65535, with Internal Reference
±
3
mV/V
AC Performance
Voltage Output Slew Rate
(Note 4)
q
±
0.3
±
0.7
V/
µ
s
Voltage Output Settling Time
(Note 4) to 0.0015% (16-Bit Settling Time), V
CC
= 5V
20
µ
s
(Note 4) to 0.012% (13-Bit Settling Time), V
CC
= 5V
10
µ
s
Digital Feedthrough
(Note 5)
0.3
nV -s
Midscale Glitch Impulse
DAC Switched Between 8000
H
and 7FFF
H
12
nV-s
Output Voltage Noise
LTC1655, At 1kHz
280
nV
Hz
Spectral Density
LTC1655L, At 1kHz
220
nV
Hz
Reference Output
Reference Output Voltage
LTC1655
q
2.036
2.048
2.060
V
LTC1655L
q
1.240
1.250
1.260
V
Reference Input Range
(Notes 6, 7) LTC1655
2.2
V
CC
/2
V
LTC1655L
1.3
V
CC
/2
V
Reference Output Tempco
LTC1655
5
ppm/
°
C
LTC1655L
10
ppm/
°
C
Reference Input Resistance
LTC1655, REF Overdriven to 2.2V
q
8.5
13
k
LTC1655L, REF Overdriven to 1.3V
q
7.0
13
k
Reference Short-Circuit Current
q
40
100
mA
Reference Output Line Regulation
±
1.5
mV/V
Reference Load Regulation
I
OUT
= 100
µ
A
q
5
mV/A
Reference Output Voltage Noise
LTC1655, At 1kHz
150
nV
Hz
Spectral Density
LTC1655L, At 1kHz
115
nV
Hz
Digital I/O
V
IH
Digital Input High Voltage
LTC1655
q
2.4
V
LTC1655L
q
2.0
V
V
IL
Digital Input Low Voltage
LTC1655
q
0.8
V
LTC1655L
q
0.6
V
V
OH
Digital Output High Voltage
LTC1655, I
OUT
= 1mA
q
V
CC
1.0
V
LTC1655L, I
OUT
= 1mA
q
V
CC
0.7
V
V
OL
Digital Output Low Voltage
LTC1655, I
OUT
= 1mA
q
0.4
V
LTC1655L, I
OUT
= 1mA
q
0.4
V
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
4
LTC1655/LTC1655L
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25
°
C.
V
CC
= 4.5V to 5.5V (LTC1655), V
CC
= 2.7V to 5.5V (LTC1655L); V
OUT
unloaded, REF unloaded, unless otherwise noted.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Nonlinearity is defined from code 128 to code 65535 (full scale).
See Applications Information.
Note 3: DAC switched between all 1s and all 0s. V
FS
= 4.096V.
Note 4: Digital inputs at 0V or V
CC
.
Note 5: Part is clocked with pin toggling between 1s and 0s, CS/LD is low.
Note 6: Reference can be overdriven (see Applications Information).
Note 7: Guaranteed by design. Not subject to test.
Note 8: Guaranteed by correlation for other reference and supply
conditions.
I
LEAK
Digital Input Leakage
V
IN
= GND to V
CC
q
±
10
µ
A
C
IN
Digital Input Capacitance
(Note 7)
10
pF
Switching
t
1
D
IN
Valid to CLK Setup
LTC1655
q
40
ns
LTC1655L
q
60
ns
t
2
D
IN
Valid to CLK Hold
LTC1655
q
0
ns
LTC1655L
q
0
ns
t
3
CLK High Time
LTC1655
q
40
ns
LTC1655L
q
60
ns
t
4
CLK Low Time
LTC1655
q
40
ns
LTC1655L
q
60
ns
t
5
CS/LD Pulse Width
LTC1655
q
50
ns
LTC1655L
q
80
ns
t
6
LSB CLK to CS/LD
LTC1655
q
40
ns
LTC1655L
q
60
ns
t
7
CS/LD Low to CLK
LTC1655
q
20
ns
LTC1655L
q
30
ns
t
8
D
OUT
Output Delay
LTC1655, C
LOAD
= 15pF
q
20
120
ns
LTC1655L, C
LOAD
= 15pF
q
20
300
ns
t
9
CLK Low to CS/LD Low
LTC1655
q
20
ns
LTC1655L
q
30
ns
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
5
LTC1655/LTC1655L
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
DIGITAL INPUT CODE
0
DIFFERENTIAL NONLINEARITY (LSB)
65,535
1655/55L G01
16,384
32,768
49,152
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.8
1.0
TC1655 Differential Nonlinearity
LOAD CURRENT (mA)
0
V
CC
V
OUT
(V)
1.2
1.0
0.8
0.6
0.4
0.2
0
1655/55L G03
5
10
15
125
°
C
25
°
C
55
°
C
V
OUT
< 1LSB
V
OUT
= 4.096V
CODE: ALL 1's
DIGITAL INPUT CODE
0
INTEGRAL NONLINEARITY (LSB)
65,535
1655/55L G02
16,384
32,768
49,152
10
8
6
4
2
0
2
4
6
8
10
LTC1655 Integral Nonlinearity
LTC1655 Minimum Supply
Headroom for Full Output Swing
vs Load Current
V
CC
= 5V (LTC1655), V
CC
= 3V (LTC1655L) unless otherwise noted.
LTC1655L Differential Nonlinearity
LTC1655L Integral Nonlinearity
LTC1655L Minimum Supply
Headroom for Full Output Swing
vs Load Current
DIGITAL INPUT CODE
0
DIFFERENTIAL NONLINEARITY (LSB)
65,535
1655/55L G01a
16,384
32,768
49,152
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.8
1.0
DIGITAL INPUT CODE
128
INTEGRAL NONLINEARITY (LSB)
65,535
1655/55L G02a
16,480
32,832
49,184
10
8
6
4
2
0
2
4
6
8
10
LOAD CURRENT (mA)
0
V
CC
V
OUT
(V)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1655/55L G03a
5
10
15
V
OUT
< 1LSB
V
OUT
= 2.5V
CODE: ALL 1's
125
°
C
25
°
C
55
°
C
6
LTC1655/LTC1655L
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
OUTPUT SINK CURRENT (mA)
0
OUTPUT PULL-DOWN VOLTAGE (V)
1.0
0.8
0.6
0.4
0.2
0
1655/55L G04
5
10
15
125
°
C
25
°
C
55
°
C
CODE: ALL 0s
LTC1655 Minimum Output Voltage
vs Output Sink Current
LTC1655 Full-Scale Voltage vs
Temperature
TEMPERATURE (
°
C)
55
FULL-SCALE VOLTAGE (V)
4.10
4.09
4.08
4.07
25
5
35
65
1655/55L G05
95
125
LTC1655L Minimum Output
Voltage vs Output Sink Current
TEMPERATURE (
°
C)
55
OFFSET (mV)
125
1655/55L G06
10
35
80
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.8
1.0
LTC1655 Offset vs Temperature
LTC1655L Full-Scale Voltage vs
Temperature
LTC1655L Offset vs Temperature
TEMPERATURE (
°
C)
55
FULL-SCALE VOLTAGE (V)
2.510
2.505
2.500
2.495
2.490
25
5
35
65
1655/55L G05a
95
125
OUTPUT SINK CURRENT (mA)
0
OUTPUT PULL-DOWN VOLTAGE (V)
0.8
0.6
0.4
0.2
0
1655/55L G04a
5
10
15
CODE: ALL 0s
125
°
C
25
°
C
55
°
C
TEMPERATURE (
°
C)
55
OFFSET (mV)
125
1655/55L G06a
10
35
80
0.6
0.5
0.4
0.3
0.2
0.1
0
V
CC
= 5V (LTC1655), V
CC
= 3V (LTC1655L) unless otherwise noted.
7
LTC1655/LTC1655L
TEMPERATURE (
°
C)
55
SUPPLY CURRENT (
µ
A)
15
25
45
125
1655/55L G08
35
5
65
85 105
700
680
660
640
620
600
580
V
CC
= 5.5V
V
CC
= 5V
V
CC
= 4.5V
LTC1655 Supply Current vs
Temperature
LOGIC INPUT VOLTAGE (V)
0
SUPPLY CURRENT (mA)
3.0
2.6
2.2
1.8
1.4
1.0
0.6
4
1655/55L G07
1
2
3
5
LTC1655 Supply Current vs
Logic Input Voltage
V
CC
= 5V (LTC1655), V
CC
= 3V (LTC1655L) unless otherwise noted.
LTC1655L Supply Current vs
Temperature
LTC1655L Supply Current vs
Logic Input Voltage
LOGIC INPUT VOLTAGE (V)
0
1
2
3
SUPPLY CURRENT (mA)
1.0
0.8
0.6
0.4
1655/55L G07a
TEMPERATURE (
°
C)
55
SUPPLY CURRENT (
µ
A)
15
25
45
125
1655/55L G08a
35
5
65
85 105
580
560
540
520
500
480
460
V
CC
= 3.3V
V
CC
= 3V
V
CC
= 2.7V
LTC1655 Large-Signal Transient
Response
LTC1655L Large-Signal Transient
Response
TIME (5
µ
s/DIV)
OUTPUT VOLTAGE (V)
1655/55L G10
3
2
1
0
V
OUT
UNLOADED
T
A
= 25
°
C
TIME (5
µ
s/DIV)
OUTPUT VOLTAGE (V)
1655/55L G09
5
4
3
2
1
0
V
OUT
UNLOADED
T
A
= 25
°
C
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
8
LTC1655/LTC1655L
PI
N
FU
N
CTIO
N
S
U
U
U
CLK (Pin 1): The TTL Level Input for the Serial Interface
Clock.
D
IN
(Pin 2): The TTL Level Input for the Serial Interface
Data. Data on the D
IN
pin is latched into the shift register
on the rising edge of the serial clock and is loaded MSB
first. The LTC1655/LTC1655L requires a 16-bit word.
CS/LD (Pin 3): The TTL Level Input for the Serial Inter-
face Enable and Load Control. When CS/LD is low, the
CLK signal is enabled, so the data can be clocked in.
When CS/LD is pulled high, data is loaded from the shift
register into the DAC register, updating the DAC output.
D
OUT
(Pin 4): Output of the Shift Register. Becomes valid
on the rising edge of the serial clock and swings from GND
to V
CC
.
GND (Pin 5): Ground.
REF (Pin 6): Reference. Output of the internal reference is
2.048V (LTC1655), 1.25V (LTC1655L). There is a gain of
two from this pin to the output. The reference can be
overdriven from 2.2V to V
CC
/2 (LTC1655) and 1.3V to
V
CC
/2 (LTC1655L). When tied to V
CC
/2, the output will
swing from GND to V
CC
. The output can only swing to
within its offset specification of V
CC
(see Applications
Information).
V
OUT
(Pin 7): Deglitched Rail-to-Rail Voltage Output. V
OUT
clears to 0V on power-up.
V
CC
(Pin 8): Positive Supply Input. 4.5V
V
CC
5.5V
(LTC1655), 2.7V
V
CC
5.5V (LTC1655L). Requires a
0.1
µ
F bypass capacitor to ground.
TI I G DIAGRA
W U
W
D15
MSB
D14
D13
D1
t
1
t
6
D0
LSB
t
2
t
4
t
3
t
8
CLK
D
IN
D
OUT
CS/LD
t
5
1655/55L TD
D15
PREVIOUS WORD
D14
PREVIOUS WORD
D0
PREVIOUS WORD
D15
CURRENT WORD
D13
PREVIOUS WORD
t
9
t
7
1
2
3
15
16
9
LTC1655/LTC1655L
DEFI ITIO S
U
U
Differential Nonlinearity (DNL): The difference between
the measured change and the ideal 1LSB change for any
two adjacent codes. The DNL error between any two codes
is calculated as follows:
DNL = (
V
OUT
LSB)/LSB
Where
V
OUT
is the measured voltage difference between
two adjacent codes.
Digital Feedthrough: The glitch that appears at the analog
output caused by AC coupling from the digital inputs when
they change state. The area of the glitch is specified in
(nV)(sec).
Full-Scale Error (FSE): The deviation of the actual full-
scale voltage from ideal. FSE includes the effects of offset
and gain errors (see Applications Information).
Gain Error (GE): The difference between the full-scale
output of a DAC from its ideal full-scale value after offset
error has been adjusted.
Integral Nonlinearity (INL): The deviation from a straight
line passing through the endpoints of the DAC transfer
curve (Endpoint INL). Because the output cannot go below
zero, the linearity is measured between full scale and the
lowest code that guarantees the output will be greater than
zero. The INL error at a given input code is calculated as
follows:
INL = [V
OUT
V
OS
(V
FS
V
OS
)(code/65535)]/LSB
Where V
OUT
is the output voltage of the DAC measured at
the given input code.
Least Significant Bit (LSB): The ideal voltage difference
between two successive codes.
LSB = 2V
REF
/65536
Resolution (n): Defines the number of DAC output states
(2
n
) that divide the full-scale range. Resolution does not
imply linearity.
Voltage Offset Error (V
OS
): Nominally, the voltage at the
output when the DAC is loaded with all zeros. A single
supply DAC can have a true negative offset, but the output
cannot go below zero (see Applications Information).
For this reason, single supply DAC offset is measured at
the lowest code that guarantees the output will be greater
than zero.
OPERATIO
U
Serial Interface
The data on the D
IN
input is loaded into the shift register
on the rising edge of the clock. The MSB is loaded first. The
DAC register loads the data from the shift register when
CS/LD is pulled high. The clock is disabled internally when
CS/LD is high. Note: CLK must be low before CS/LD is
pulled low to avoid an extra internal clock pulse. The input
word must be 16 bits wide.
The buffered output of the 16-bit shift register is available
on the D
OUT
pin which swings from GND to V
CC
.
Multiple LTC1655s/LTC1655Ls may be daisy-chained to-
gether by connecting the D
OUT
pin to the D
IN
pin of the next
chip while the clock and CS/LD signals remain common to
all chips in the daisy chain. The serial data is clocked to all
of the chips, then the CS/LD signal is pulled high to update
all of them simultaneously. The shift register and DAC
register are cleared to all 0s on power-up.
Voltage Output
The LTC1655/LTC1655L rail-to-rail buffered output can
source or sink 5mA over the entire operating temperature
range while pulling to within 600mV of the positive supply
voltage or ground. The output stage is equipped with a
deglitcher that gives a midscale glitch of 12nV-s. At power-
up, the output clears to 0V.
The output swings to within a few millivolts of either sup-
ply rail when unloaded and has an equivalent output resis-
tance of 40
(70
for the LTC1655L) when driving a load
to the rails. The output can drive 1000pF without going into
oscillation.
10
LTC1655/LTC1655L
APPLICATIO
N
S I
N
FOR
M
ATIO
N
W
U
U
U
Rail-to-Rail Output Considerations
In any rail-to-rail DAC, the output swing is limited to
voltages within the supply range.
If the DAC offset is negative, the output for the lowest
codes limits at 0V as shown in Figure 1b.
Similarly, limiting can occur near full-scale when the REF
pin is tied to V
CC
/2. If V
REF
= V
CC
/2 and the DAC full-scale
error (FSE) is positive, the output for the highest codes
limits at V
CC
as shown in Figure 1c. No full-scale limiting
can occur if V
REF
is less than (V
CC
FSE)/2.
Offset and linearity are defined and tested over the region
of the DAC transfer function where no output limiting can
occur.
Figure 1. Effects of Rail-to-Rail Operation On a DAC Transfer Curve. (a) Overall Transfer Function (b) Effect of Negative
Offset for Codes Near Zero Scale (c) Effect of Positive Full-Scale Error for Input Codes Near Full Scale When V
REF
= V
CC
/2
1655/55L F01
INPUT CODE
OUTPUT
VOLTAGE
NEGATIVE
OFFSET
0V
32768
0
65535
INPUT CODE
OUTPUT
VOLTAGE
V
REF
= V
CC
/2
V
CC
V
CC
V
REF
= V
CC
/2
INPUT CODE
OUTPUT
VOLTAGE
POSITIVE
FSE
(1b)
(1a)
(1c)
11
LTC1655/LTC1655L
TYPICAL APPLICATIO
N
S
U
This circuit shows how to use an LTC1655 to make an
optoisolated digitally controlled 4mA to 20mA process
controller. The controller circuitry, including the
optoisolation, is powered by the loop voltage that can have
a wide range of 6V to 30V. The 2.048V reference output of
the LTC1655 is used for the 4mA offset current and V
OUT
is used for the digitally controlled 0mA to 16mA current.
R
S
is a sense resistor and the op amp modulates the
transistor Q1 to provide the 4mA to 20mA current through
this resistor. The potentiometers allow for offset and full-
scale adjustment. The control circuitry dissipates well
under the 4mA budget at zero scale.
1655/55L TA03
3k
10k
1k
75k
1%
5k
150k
1%
20k
Q1
2N3440
R
S
10
V
LOOP
6V TO 30V
I
OUT
OUT
IN
CLK
D
IN
CS/LD
CLK
D
IN
CS/LD
CLK
D
IN
CS/LD
V
CC
V
OUT
1
µ
F
LTC1655
4N28
OPTOISOLATORS
5V
500
LT
®
1121-5
FROM
OPTOISOLATED
INPUTS
V
REF
GND
+
LT
®
1077
1
8
6
5
7
2
3
6
7
4
3
2
An Isolated 4mA to 20mA Process Controller
12
LTC1655/LTC1655L
TYPICAL APPLICATIO
N
S
U
This circuit shows how to make a bipolar output 16-bit
DAC with a wide output swing using an LTC1655 and an
LT1077. R1 and R2 resistively divide down the LTC1655
output and an offset is summed in using the LTC1655
onboard 2.048V reference and R3 and R4. R5 ensures that
the onboard reference is always sourcing current and
never has to sink any current even when V
OUT
is at full
scale. The LT1077 output will have a wide bipolar output
swing of 4.096V to 4.096V as shown in the figure below.
With this output swing 1LSB = 125
µ
V.
A Wide Swing, Bipolar Output 16-Bit DAC
CLK
D
IN
CS/LD
µ
P
0.1
µ
F
V
CC
V
OUT
GND
V
REF
R1
100k
1%
5V
LTC1655
1655/55L TA05
+
LT1077
5V
5V
R2
200k
1%
R3
100k
1%
R5
100k
1%
R4
200k
1%
(2)(D
IN
)(4.096)
65536
V
OUT
:
D
IN
V
OUT
4.096
4.096
32768
0
65535
TRANSFER CURVE
4.096V
1
6
8
5
7
2
3
6
7
4
3
2
13
LTC1655/LTC1655L
TYPICAL APPLICATIO
N
S
U
This circuit shows a digitally programmable current source
from an external voltage source using an external op amp,
an LT1218 and an NPN transistor (2N3440). Any digital
word from 0 to 65535 is loaded into the LTC1655 and its
output correspondingly swings from 0V to 4.096V. This
voltage will be forced across the resistor R
A
. If R
A
is
chosen to be 412
, the output current will range from
0mA at zero scale to 10mA at full scale. The minimum
voltage for V
S
is determined by the load resistor R
L
and
Q1's V
CESAT
voltage. With a load resistor of 50
, the
voltage source can be 5V.
CLK
D
IN
CS/LD
0.1
µ
F
V
CC
V
OUT
GND
5V
LTC1655
µ
P
1655/55L TA04
+
LT1218
5V < V
S
< 100V
FOR R
L
50
Q1
2N3440
R
A
412
1%
R
L
I
OUT
=
0mA TO 10mA
(D
IN
)(4.096)
(65536)(R
A
)
1
8
5
7
2
3
6
7
4
3
2
Digitally Programmable Current Source
14
LTC1655/LTC1655L
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
N
U
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
N8 1098
0.100
(2.54)
BSC
0.065
(1.651)
TYP
0.045 0.065
(1.143 1.651)
0.130
±
0.005
(3.302
±
0.127)
0.020
(0.508)
MIN
0.018
±
0.003
(0.457
±
0.076)
0.125
(3.175)
MIN
1
2
3
4
8
7
6
5
0.255
±
0.015*
(6.477
±
0.381)
0.400*
(10.160)
MAX
0.009 0.015
(0.229 0.381)
0.300 0.325
(7.620 8.255)
0.325
+0.035
0.015
+0.889
0.381
8.255
(
)
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
15
LTC1655/LTC1655L
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
N
U
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.016 0.050
(0.406 1.270)
0.010 0.020
(0.254 0.508)
×
45
°
0
°
8
°
TYP
0.008 0.010
(0.203 0.254)
SO8 1298
0.053 0.069
(1.346 1.752)
0.014 0.019
(0.355 0.483)
TYP
0.004 0.010
(0.101 0.254)
0.050
(1.270)
BSC
1
2
3
4
0.150 0.157**
(3.810 3.988)
8
7
6
5
0.189 0.197*
(4.801 5.004)
0.228 0.244
(5.791 6.197)
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
16
LTC1655/LTC1655L
©
LINEAR TECHNOLOGY CORPORATION 1998
16555lf LT/TP 0800 4K · PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
q
FAX: (408) 434-0507
q
www.linear-tech.com
PART
NUMBER
DESCRIPTION
COMMENTS
LTC1257
Single 12-Bit V
OUT
DAC, Full Scale: 2.048V, V
CC
: 4.75V to 15.75V,
5V to 15V Single Supply, Complete V
OUT
DAC SO-8 Package
in Reference Can Be Overdriven Up to 12V, i.e., FS
MAX
= 12V
LTC1446/
Dual 12-Bit V
OUT
DACs in SO-8 Package
LTC1446: V
CC
= 4.5V to 5.5V, V
OUT
= 0V to 4.095V
LTC1446L
LTC1446L: V
CC
= 2.7V to 5.5V, V
OUT
= 0V to 2.5V
LTC1448
Dual 12-Bit V
OUT
DAC, V
CC
: 2.7V to 5.5V
Output Swings from GND to REF. REF Input Can Be Tied to V
CC
LTC1450/
Single 12-Bit V
OUT
DACs with Parallel Interface
LTC1450: V
CC
= 4.5V to 5.5V, V
OUT
= 0V to 4.095V
LTC1450L
LTC1450L: V
CC
= 2.7V to 5.5V, V
OUT
= 0V to 2.5V
LTC1451
Single Rail-to-Rail 12-Bit DAC, Full Scale: 4.095V, V
CC
: 4.5V to 5.5V,
5V, Low Power Complete V
OUT
DAC in SO-8 Package
Internal 2.048V Reference Brought Out to Pin
LTC1452
Single Rail-to-Rail 12-Bit V
OUT
Multiplying DAC, V
CC
: 2.7V to 5.5V
Low Power, Multiplying V
OUT
DAC with Rail-to-Rail
Buffer Amplifier in SO-8 Package
LTC1453
Single Rail-to-Rail 12-Bit V
OUT
DAC, Full Scale: 2.5V, V
CC
: 2.7V to 5.5V 3V, Low Power, Complete V
OUT
DAC in SO-8 Package
LTC1454/
Dual 12-Bit V
OUT
DACs in SO-16 Package with Added Functionality
LTC1454: V
CC
= 4.5V to 5.5V, V
OUT
= 0V to 4.095V
LTC1454L
LTC1454L: V
CC
= 2.7V to 5.5V, V
OUT
= 0V to 2.5V
LTC1456
Single Rail-to-Rail Output 12-Bit DAC with Clear Pin,
Low Power, Complete V
OUT
DAC in SO-8
Full Scale: 4.095V, V
CC
: 4.5V to 5.5V
Package with Clear Pin
LTC1458/
Quad 12 Bit Rail-to-Rail Output DACs with Added Functionality
LTC1458: V
CC
= 4.5V to 5.5V, V
OUT
= 0V to 4.095V
LTC1458L
LTC1458L: V
CC
= 2.7V to 5.5V, V
OUT
= 0V to 2.5V
LTC1650
Single 16-Bit V
OUT
Industrial DAC in 16-Pin SO, V
CC
=
±
5V
Low Power, Deglitched, 4-Quadrant Mulitplying V
OUT
DAC,
Output Swing
±
4.5V
LTC1654
Dual 14-Bit DAC
1LSB DNL, 2 DACs in SO-8 Footprint
LTC1657/
Single 16-Bit V
OUT
DAC with Parallel Interface
LTC1657: V
CC
= 5V, Low Power, Deglitched, V
OUT
= 0V to 4.096V
LTC1657L
LTC1657L: V
CC
= 3V, Low Power, Deglitched, V
OUT
= 0V to 2.5V
LTC1658
Single Rail-to-Rail 14-Bit V
OUT
DAC in 8-Pin MSOP,
Low Power, Multiplying V
OUT
DAC in MS8 Package. Output
V
CC
= 2.7V to 5.5V
Swings from GND to REF. REF Input Can Be Tied to V
CC
LTC1659
Single Rail-to-Rail 12-Bit V
OUT
DAC in 8-Pin MSOP,
Low Power, Multiplying V
OUT
DAC in MS8 Package. Output
V
CC
= 2.7V to 5.5V
Swings from GND to REF. REF Input Can Be Tied to V
CC
RELATED PARTS
TYPICAL APPLICATIO
N
U
CLK
D
IN
CS/LD
µ
P
0.1
µ
F
V
CC
V
OUT
GND
R1
100k
5V
5V
LTC1655/
LTC1655L
1655/55L TA06
1
8
5
7
2
3
This circuit shows how to measure negative offset. Since
LTC1655/LTC1655L operate on a single supply, if its
offset is negative, the output for code 0 limits to 0V. To
measure this negative offset, a negative supply is needed.
Connect resistor R1 as shown in the figure below. The
output voltage is the offset when code 0 is loaded in.
Negative Offset Measurement
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