1
LTC1655/LTC1655L
16-Bit Rail-to-Rail
Micropower DACs in
SO-8 Package
16-Bit Monotonicity Over Temperature
Deglitched Rail-to-Rail Voltage Output
SO-8 Package
I
CC(TYP)
: 600µA
Internal Reference: 2.048V (LTC1655)
1.25V (LTC1655L)
Maximum DNL Error: ±1LSB
Settling Time: 20µS to ±1LSB
750kHz Max Update Rate
Power-On Reset to Zero Volts
3-Wire Cascadable Serial Interface
Low Cost
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.
Digital Calibration
Industrial Process Control
Automatic Test Equipment
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
µP
D
IN
V
CC
16
REF
2
86
D
OUT
4
5
1655/55L TA01
CLK1
CS/LD3 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
UU
W
2
LTC1655/LTC1655L
ABSOLUTE MAXIMUM RATINGS
W
WW
U
ORDER PART
NUMBER
WU
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
TJMAX = 125°C, θJA = 100°C/W (N8)
TJMAX = 125°C, θJA = 150°C/W (S8)
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 4.5V to 5.5V (LTC1655), VCC = 2.7V to 5.5V (LTC1655L); VOUT unloaded, REF unloaded, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DAC
Resolution 16 Bits
Monotonicity 16 Bits
DNL Differential Nonlinearity Guaranteed Monotonic (Note 2)
LTC1655, REF = 2.2V, V
CC
= 5V (Note 8) (External) ±0.3 ±1.0 LSB
LTC1655L, REF = 2.2V, V
CC
= 5V (Note 8) (External) ±0.5 ±1.0 LSB
INL Integral Nonlinearity LTC1655, REF = 2.2V, V
CC
= 5V (Note 8) (External) ±8±20 LSB
LTC1655L, REF = 2.2V, V
CC
= 5V (Note 8) (External) ±8±20 LSB
ZSE Zero Scale Error LTC1655 0 3.0 mV
LTC1655L 0 3.5 mV
V
OS
Offset Error Measured at Code 200
LTC1655, REF = 2.2V, V
CC
= 5V (Note 8) (External) ±0.5 ±3.0 mV
LTC1655L, REF = 1.3V, V
CC
= 2.7V (Note 8) (External) ±0.5 ±3.5 mV
V
OS
TC Offset Error Tempco ±5µV/°C
Gain Error REF = 2.2V (External), V
CC
= 5V (Note 8) ±5±16 LSB
Gain Error Drift 0.5 ppm/°C
Power Supply
V
CC
Positive Supply Voltage For Specified Performance
LTC1655 4.5 5.5 V
LTC1655L 2.7 5.5 V
I
CC
Supply Current (Note 3) 600 1200 µA
3
LTC1655/LTC1655L
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 4.5V to 5.5V (LTC1655), VCC = 2.7V to 5.5V (LTC1655L); VOUT unloaded, REF unloaded, unless otherwise noted.
Op Amp DC Performance
Short-Circuit Current Low V
OUT
Shorted to GND
LTC1655 70 120 mA
LTC1655L 70 140 mA
Short-Circuit Current High V
OUT
Shorted to V
CC
LTC1655 80 140 mA
LTC1655L 70 150 mA
Output Impedance to GND Input Code = 0
LTC1655 40 120
LTC1655L 70 160
Output Line Regulation Input Code = 65535, with Internal Reference ±3 mV/V
AC Performance
Voltage Output Slew Rate (Note 4) ±0.3 ±0.7 V/µs
Voltage Output Settling Time (Note 4) to 0.0015% (16-Bit Settling Time), V
CC
= 5V 20 µs
(Note 4) to 0.012% (13-Bit Settling Time), V
CC
= 5V 10 µs
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 nVHz
Spectral Density LTC1655L, At 1kHz 220 nVHz
Reference Output
Reference Output Voltage LTC1655 2.036 2.048 2.060 V
LTC1655L 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 8.5 13 k
LTC1655L, REF Overdriven to 1.3V 7.0 13 k
Reference Short-Circuit Current 40 100 mA
Reference Output Line Regulation ±1.5 mV/V
Reference Load Regulation I
OUT
= 100µA5 mV/A
Reference Output Voltage Noise LTC1655, At 1kHz 150 nVHz
Spectral Density LTC1655L, At 1kHz 115 nVHz
Digital I/O
V
IH
Digital Input High Voltage LTC1655 2.4 V
LTC1655L 2.0 V
V
IL
Digital Input Low Voltage LTC1655 0.8 V
LTC1655L 0.6 V
V
OH
Digital Output High Voltage LTC1655, I
OUT
= –1mA V
CC
– 1.0 V
LTC1655L, I
OUT
= – 1mA V
CC
– 0.7 V
V
OL
Digital Output Low Voltage LTC1655, I
OUT
= 1mA 0.4 V
LTC1655L, I
OUT
= 1mA 0.4 V
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
4
LTC1655/LTC1655L
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 4.5V to 5.5V (LTC1655), VCC = 2.7V to 5.5V (LTC1655L); VOUT 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
±10 µA
C
IN
Digital Input Capacitance (Note 7) 10 pF
Switching
t
1
D
IN
Valid to CLK Setup LTC1655 40 ns
LTC1655L 60 ns
t
2
D
IN
Valid to CLK Hold LTC1655 0ns
LTC1655L 0ns
t
3
CLK High Time LTC1655 40 ns
LTC1655L 60 ns
t
4
CLK Low Time LTC1655 40 ns
LTC1655L 60 ns
t
5
CS/LD Pulse Width LTC1655 50 ns
LTC1655L 80 ns
t
6
LSB CLK to CS/LD LTC1655 40 ns
LTC1655L 60 ns
t
7
CS/LD Low to CLK LTC1655 20 ns
LTC1655L 30 ns
t
8
D
OUT
Output Delay LTC1655, C
LOAD
= 15pF 20 120 ns
LTC1655L, C
LOAD
= 15pF 20 300 ns
t
9
CLK Low to CS/LD Low LTC1655 20 ns
LTC1655L 30 ns
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
5
LTC1655/LTC1655L
TYPICAL PERFORMANCE CHARACTERISTICS
UW
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
510 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
VCC = 5V (LTC1655), VCC = 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
510 15
V
OUT
< 1LSB
V
OUT
= 2.5V
CODE: ALL 1’s 125°C
25°C
–55°C
6
LTC1655/LTC1655L
TYPICAL PERFORMANCE CHARACTERISTICS
UW
OUTPUT SINK CURRENT (mA)
0
OUTPUT PULL-DOWN VOLTAGE (V)
1.0
0.8
0.6
0.4
0.2
0
1655/55L G04
510 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 53565
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 53565
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
510 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
VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted.
7
LTC1655/LTC1655L
TEMPERATURE (°C)
–55
SUPPLY CURRENT (µA)
–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
1235
LTC1655 Supply Current vs
Logic Input Voltage
VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted.
LTC1655L Supply Current vs
Temperature
LTC1655L Supply Current vs
Logic Input Voltage
LOGIC INPUT VOLTAGE (V)
0123
SUPPLY CURRENT (mA)
1.0
0.8
0.6
0.4
1655/55L G07a
TEMPERATURE (°C)
–55
SUPPLY CURRENT (µA)
–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 (5µs/DIV)
OUTPUT VOLTAGE (V)
1655/55L G10
3
2
1
0
V
OUT
UNLOADED
T
A
= 25°C
TIME (5µs/DIV)
OUTPUT VOLTAGE (V)
1655/55L G09
5
4
3
2
1
0
V
OUT
UNLOADED
T
A
= 25°C
TYPICAL PERFORMANCE CHARACTERISTICS
UW
8
LTC1655/LTC1655L
PIN FUNCTIONS
UUU
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
0.1µF bypass capacitor to ground.
TI I G DIAGRA
WU 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
12 3 15 16
9
LTC1655/LTC1655L
DEFI ITIO S
UU
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 = [VOUT – VOS – (VFS – VOS)(code/65535)]/LSB
Where VOUT 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
APPLICATIONS INFORMATION
WUUU
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 VREF = VCC/2
1655/55L F01
INPUT CODE
OUTPUT
VOLTAGE
NEGATIVE
OFFSET
0V
327680 65535
INPUT CODE
OUTPUT
VOLTAGE
VREF = VCC/2
VCC
VCC
VREF = VCC /2
INPUT CODE
OUTPUT
VOLTAGE
POSITIVE
FSE
(1b)
(1a)
(1c)
11
LTC1655/LTC1655L
TYPICAL APPLICATIONS
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
OUTIN
CLK
D
IN
CS/LD
CLK
D
IN
CS/LD
CLK
D
IN
CS/LD
V
CC
V
OUT
1µF
LTC1655
4N28
OPTOISOLATORS
5V
500
LT
®
1121-5
FROM
OPTOISOLATED
INPUTS
V
REF
GND
+
LT
®
1077
1
86
5
7
2
36
7
4
3
2
An Isolated 4mA to 20mA Process Controller
12
LTC1655/LTC1655L
TYPICAL APPLICATIONS
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 = 125µV.
A Wide Swing, Bipolar Output 16-Bit DAC
CLK
DIN
CS/LD
µP
0.1µF
VCC
VOUT
GND VREF
R1
100k
1%
5V
LTC1655
1655/55L TA05
+
LT1077
5V
–5V
R2
200k
1%
R3
100k
1%
R5
100k
1%
R4
200k
1%
(2)(DIN)(4.096)
65536
VOUT:
DIN
VOUT
4.096
4.096
32768
065535
TRANSFER CURVE – 4.096V
1
6
8
5
7
2
3
6
7
4
3
2
13
LTC1655/LTC1655L
TYPICAL APPLICATIONS
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
0.1µF
V
CC
V
OUT
GND
5V
LTC1655
µP
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
36
7
4
3
2
Digitally Programmable Current Source
14
LTC1655/LTC1655L
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTION
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
12 34
87 65
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 DESCRIPTION
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
1234
0.150 – 0.157**
(3.810 – 3.988)
8765
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
FAX: (408) 434-0507
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 APPLICATION
U
CLK
D
IN
CS/LD
µP
0.1µF
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