Linear Dimensions LTC1655LIS8 16-bit rail-to-rail micropower dacs in so-8 package Datasheet

LTC1655/LTC1655L
16-Bit Rail-to-Rail
Micropower DACs in
SO-8 Package
U
DESCRIPTIO
FEATURES
■
■
■
■
■
■
■
■
■
■
■
■
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
MICROWIRETM protocols. The CLK input has a Schmitt
trigger that allows direct optocoupler interface.
16-Bit Monotonicity Over Temperature
Deglitched Rail-to-Rail Voltage Output
SO-8 Package
ICC(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 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.
U
APPLICATIO S
■
■
■
■
The LTC1655/LTC1655L are pin compatible with Linear
Technology’s 12-bit VOUT 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.
W
FU CTIO AL BLOCK DIAGRA
U
U
Functional Block Diagram: 16-Bit Rail-to-Rail DAC
LTC1655: 4.5V TO 5.5V
LTC1655L: 2.7V TO 5.5V
8
LTC1655: 2.048V
LTC1655L: 1.25V
6
0.6
16-BIT
SHIFT
REG
AND
DAC
LATCH
16
16-BIT
DAC
+
VOUT 7
–
DNL ERROR (LSB)
3 CS/LD
0.8
REF
2 DIN
µP
1.0
REF
VCC
1 CLK
Differential Nonlinearity
vs Input Code
0.4
0.2
0
– 0.2
– 0.4
– 0.6
4 DOUT
– 0.8
TO
OTHER
DACS
POWER-ON
RESET
– 1.0
0
GND
5
16384
32768
CODE
49152
65535
1655/55L TA01
1655/55L TA02
1
LTC1655/LTC1655L
W
U
U
W W
U
W
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER I FOR ATIO
(Note 1)
VCC to GND .............................................. – 0.5V to 7.5V
TTL Input Voltage .................................... – 0.5V to 7.5V
VOUT, REF ....................................... – 0.5V to VCC + 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
ORDER PART
NUMBER
TOP VIEW
CLK 1
8
VCC
DIN 2
7
VOUT
CS/LD 3
6
REF
DOUT 4
5
GND
N8 PACKAGE
8-LEAD PDIP
LTC1655CN8
LTC1655IN8
LTC1655CS8
LTC1655IS8
LTC1655LCN8
LTC1655LIN8
LTC1655LCS8
LTC1655LIS8
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 100°C/W (N8)
TJMAX = 125°C, θJA = 150°C/W (S8)
S8 PART MARKING
1655
1655I
1655L
1655LI
Consult factory for Military grade parts.
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.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DAC
DNL
Resolution
●
16
Bits
Monotonicity
●
16
Bits
Differential Nonlinearity
Guaranteed Monotonic (Note 2)
LTC1655, REF = 2.2V, VCC = 5V (Note 8) (External)
LTC1655L, REF = 2.2V, VCC = 5V (Note 8) (External)
●
●
±0.3
±0.5
±1.0
±1.0
LSB
LSB
±8
±8
±20
±20
LSB
LSB
3.0
3.5
mV
mV
±3.0
±3.5
mV
mV
INL
Integral Nonlinearity
LTC1655, REF = 2.2V, VCC = 5V (Note 8) (External)
LTC1655L, REF = 2.2V, VCC = 5V (Note 8) (External)
●
●
ZSE
Zero Scale Error
LTC1655
LTC1655L
●
●
VOS
Offset Error
Measured at Code 200
●
LTC1655, REF = 2.2V, VCC = 5V (Note 8) (External)
LTC1655L, REF = 1.3V, VCC = 2.7V (Note 8) (External) ●
VOSTC
0
0
±0.5
±0.5
±5
Offset Error Tempco
Gain Error
REF = 2.2V (External), VCC = 5V (Note 8)
±5
●
Gain Error Drift
µV/°C
±16
0.5
LSB
ppm/°C
Power Supply
VCC
ICC
2
Positive Supply Voltage
Supply Current
For Specified Performance
LTC1655
LTC1655L
●
●
(Note 3)
●
4.5
2.7
600
5.5
5.5
V
V
1200
µA
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.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Op Amp DC Performance
Short-Circuit Current Low
Short-Circuit Current High
Output Impedance to GND
Output Line Regulation
VOUT Shorted to GND
LTC1655
LTC1655L
●
●
70
70
120
140
mA
mA
VOUT Shorted to VCC
LTC1655
LTC1655L
●
●
80
70
140
150
mA
mA
Input Code = 0
LTC1655
LTC1655L
●
●
40
70
120
160
Ω
Ω
±3
mV/V
Input Code = 65535, with Internal Reference
AC Performance
±0.3
±0.7
Voltage Output Slew Rate
(Note 4)
Voltage Output Settling Time
(Note 4) to 0.0015% (16-Bit Settling Time), VCC = 5V
(Note 4) to 0.012% (13-Bit Settling Time), VCC = 5V
20
10
µs
µs
Digital Feedthrough
(Note 5)
0.3
nV-s
●
V/µs
Midscale Glitch Impulse
DAC Switched Between 8000H and 7FFFH
12
nV-s
Output Voltage Noise
Spectral Density
LTC1655, At 1kHz
LTC1655L, At 1kHz
280
220
nV√Hz
nV√Hz
Reference Output
Reference Output Voltage
LTC1655
LTC1655L
Reference Input Range
(Notes 6, 7) LTC1655
LTC1655L
Reference Output Tempco
LTC1655
LTC1655L
Reference Input Resistance
LTC1655, REF Overdriven to 2.2V
LTC1655L, REF Overdriven to 1.3V
Reference Short-Circuit Current
●
●
2.036
1.240
2.048
1.250
2.2
1.3
●
●
8.5
7.0
IOUT = 100µA
Reference Output Voltage Noise
Spectral Density
LTC1655, At 1kHz
LTC1655L, At 1kHz
VIH
Digital Input High Voltage
LTC1655
LTC1655L
●
●
VIL
Digital Input Low Voltage
LTC1655
LTC1655L
●
●
VOH
Digital Output High Voltage
LTC1655, IOUT = – 1mA
LTC1655L, IOUT = – 1mA
●
●
VOL
Digital Output Low Voltage
LTC1655, IOUT = 1mA
LTC1655L, IOUT = 1mA
●
●
VCC /2
VCC /2
V
V
ppm/°C
ppm/°C
13
13
kΩ
kΩ
Reference Output Line Regulation
Reference Load Regulation
V
V
5
10
40
●
2.060
1.260
●
100
mA
±1.5
mV/V
5
mV/A
150
115
nV√Hz
nV√Hz
Digital I/O
2.4
2.0
V
V
0.8
0.6
VCC – 1.0
VCC – 0.7
V
V
V
V
0.4
0.4
V
V
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.
SYMBOL
PARAMETER
CONDITIONS
MIN
ILEAK
Digital Input Leakage
VIN = GND to VCC
CIN
Digital Input Capacitance
(Note 7)
t1
DIN Valid to CLK Setup
LTC1655
LTC1655L
●
●
40
60
ns
ns
t2
DIN Valid to CLK Hold
LTC1655
LTC1655L
●
●
0
0
ns
ns
t3
CLK High Time
LTC1655
LTC1655L
●
●
40
60
ns
ns
t4
CLK Low Time
LTC1655
LTC1655L
●
●
40
60
ns
ns
t5
CS/LD Pulse Width
LTC1655
LTC1655L
●
●
50
80
ns
ns
t6
LSB CLK to CS/LD
LTC1655
LTC1655L
●
●
40
60
ns
ns
t7
CS/LD Low to CLK
LTC1655
LTC1655L
●
●
20
30
ns
ns
t8
DOUT Output Delay
LTC1655, CLOAD = 15pF
LTC1655L, CLOAD = 15pF
●
●
20
20
t9
CLK Low to CS/LD Low
LTC1655
LTC1655L
●
●
20
30
●
TYP
MAX
UNITS
±10
µA
10
pF
Switching
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. VFS = 4.096V.
Note 4: Digital inputs at 0V or VCC.
4
120
300
ns
ns
ns
ns
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.
LTC1655/LTC1655L
U W
TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted.
LTC1655L Differential Nonlinearity
1.0
1.0
0.8
0.8
DIFFERENTIAL NONLINEARITY (LSB)
DIFFERENTIAL NONLINEARITY (LSB)
TC1655 Differential Nonlinearity
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
0
16,384
49,152
32,768
DIGITAL INPUT CODE
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
65,535
0
16,384
49,152
32,768
DIGITAL INPUT CODE
1655/55L G01
1655/55L G01a
LTC1655L Integral Nonlinearity
10
10
8
8
INTEGRAL NONLINEARITY (LSB)
INTEGRAL NONLINEARITY (LSB)
LTC1655 Integral Nonlinearity
6
4
2
0
–2
–4
–6
6
4
2
0
–2
–4
–6
–8
–8
–10
128
–10
0
16,384
49,152
32,768
DIGITAL INPUT CODE
65,535
16,480
49,184
32,832
DIGITAL INPUT CODE
65,535
1655/55L G02a
1655/55L G02
LTC1655 Minimum Supply
Headroom for Full Output Swing
vs Load Current
LTC1655L Minimum Supply
Headroom for Full Output Swing
vs Load Current
2.0
1.2
∆VOUT < 1LSB
VOUT = 4.096V
CODE: ALL 1’s
1.0
∆VOUT < 1LSB
VOUT = 2.5V
CODE: ALL 1’s
1.8
1.6
125°C
1.4
0.8
VCC – VOUT (V)
VCC – VOUT (V)
65,535
125°C
0.6
25°C
0.4
–55°C
1.2
25°C
1.0
0.8
–55°C
0.6
0.4
0.2
0.2
0
0
10
5
LOAD CURRENT (mA)
15
1655/55L G03
0
0
10
5
LOAD CURRENT (mA)
15
1655/55L G03a
5
LTC1655/LTC1655L
U W
TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted.
LTC1655 Minimum Output Voltage
vs Output Sink Current
LTC1655L Minimum Output
Voltage vs Output Sink Current
1.0
0.8
CODE: ALL 0s
OUTPUT PULL-DOWN VOLTAGE (V)
OUTPUT PULL-DOWN VOLTAGE (V)
CODE: ALL 0s
0.8
0.6
125°C
0.4
25°C
–55°C
0.2
0
0
10
5
OUTPUT SINK CURRENT (mA)
0.6
25°C
–55°C
0.4
0.2
0
15
125°C
0
10
5
OUTPUT SINK CURRENT (mA)
1655/55L G04
1655/55L G04a
LTC1655L Full-Scale Voltage vs
Temperature
LTC1655 Full-Scale Voltage vs
Temperature
4.10
2.510
FULL-SCALE VOLTAGE (V)
FULL-SCALE VOLTAGE (V)
15
4.09
4.08
4.07
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
2.505
2.500
2.495
2.490
–55
–25
5
35
65
TEMPERATURE (°C)
1655/55L G05
95
125
1655/55L G05a
LTC1655 Offset vs Temperature
LTC1655L Offset vs Temperature
1.0
0.6
0.8
0.5
0.6
OFFSET (mV)
OFFSET (mV)
0.4
0.2
0
–0.2
0.4
0.3
0.2
–0.4
–0.6
0.1
–0.8
–1.0
–55
–10
80
35
TEMPERATURE (°C)
125
1655/55L G06
6
0
–55
–10
80
35
TEMPERATURE (°C)
125
1655/55L G06a
LTC1655/LTC1655L
U W
TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted.
LTC1655 Supply Current vs
Logic Input Voltage
LTC1655L Supply Current vs
Logic Input Voltage
1.0
3.0
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
2.6
2.2
1.8
1.4
0.8
0.6
1.0
0.4
0.6
0
1
3
4
2
LOGIC INPUT VOLTAGE (V)
0
5
1
2
LOGIC INPUT VOLTAGE (V)
1655/55L G07a
1655/55L G07
LTC1655L Supply Current vs
Temperature
700
580
680
560
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
LTC1655 Supply Current vs
Temperature
660
VCC = 5.5V
640
VCC = 5V
620
VCC = 4.5V
600
3
540
520
VCC = 3.3V
500
VCC = 3V
480
VCC = 2.7V
580
–55 –35 –15
460
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
5 25 45 65 85 105 125
TEMPERATURE (°C)
1655/55L G08
1655/55L G08a
LTC1655 Large-Signal Transient
Response
LTC1655L Large-Signal Transient
Response
5
3
VOUT UNLOADED
TA = 25°C
VOUT UNLOADED
TA = 25°C
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
4
3
2
2
1
1
0
0
TIME (5µs/DIV)
TIME (5µs/DIV)
1655/55L G09
1655/55L G10
7
LTC1655/LTC1655L
U
U
U
PIN FUNCTIONS
CLK (Pin 1): The TTL Level Input for the Serial Interface
Clock.
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 VCC/2 (LTC1655) and 1.3V to
VCC/2 (LTC1655L). When tied to VCC/2, the output will
swing from GND to VCC. The output can only swing to
within its offset specification of VCC (see Applications
Information).
DIN (Pin 2): The TTL Level Input for the Serial Interface
Data. Data on the DIN 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 Interface 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.
VOUT (Pin 7): Deglitched Rail-to-Rail Voltage Output. VOUT
clears to 0V on power-up.
VCC (Pin 8): Positive Supply Input. 4.5V ≤ VCC ≤ 5.5V
(LTC1655), 2.7V ≤ VCC ≤ 5.5V (LTC1655L). Requires a
0.1µF bypass capacitor to ground.
DOUT (Pin 4): Output of the Shift Register. Becomes valid
on the rising edge of the serial clock and swings from GND
to VCC.
WU
W
TI I G DIAGRA
t1
t9
t2
t7
CLK
DIN
1
D15
MSB
2
D14
t6
t3
t4
15
3
D13
D1
16
D0
LSB
t5
CS/LD
t8
DOUT
D15
PREVIOUS WORD
D14
PREVIOUS WORD
D13
PREVIOUS WORD
D0
PREVIOUS WORD
D15
CURRENT WORD
1655/55L TD
8
LTC1655/LTC1655L
U
U
DEFI ITIO S
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 = (∆VOUT – LSB)/LSB
Where ∆VOUT 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 fullscale 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 = 2VREF/65536
Resolution (n): Defines the number of DAC output states
(2n) that divide the full-scale range. Resolution does not
imply linearity.
Voltage Offset Error (VOS): 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.
U
OPERATIO
Serial Interface
The data on the DIN 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 DOUT pin which swings from GND to VCC.
Multiple LTC1655s/LTC1655Ls may be daisy-chained together by connecting the DOUT pin to the DIN 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 powerup, the output clears to 0V.
The output swings to within a few millivolts of either supply rail when unloaded and has an equivalent output resistance of 40Ω (70Ω for the LTC1655L) when driving a load
to the rails. The output can drive 1000pF without going into
oscillation.
9
LTC1655/LTC1655L
U
W
U
U
APPLICATIONS INFORMATION
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.
error (FSE) is positive, the output for the highest codes
limits at VCC as shown in Figure 1c. No full-scale limiting
can occur if VREF is less than (VCC – FSE)/2.
Offset and linearity are defined and tested over the region
of the DAC transfer function where no output limiting can
occur.
Similarly, limiting can occur near full-scale when the REF
pin is tied to VCC /2. If VREF = VCC /2 and the DAC full-scale
VCC
VREF = VCC /2
POSITIVE
FSE
OUTPUT
VOLTAGE
INPUT CODE
(1c)
VCC
VREF = VCC /2
OUTPUT
VOLTAGE
0
32768
INPUT CODE
65535
(1a)
OUTPUT
VOLTAGE
0V
NEGATIVE
OFFSET
INPUT CODE
(1b)
1655/55L F01
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
10
LTC1655/LTC1655L
U
TYPICAL APPLICATIONS
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 VOUT
is used for the digitally controlled 0mA to 16mA current.
RS 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 fullscale adjustment. The control circuitry dissipates well
under the 4mA budget at zero scale.
An Isolated 4mA to 20mA Process Controller
VLOOP
6V TO 30V
LT ®1121-5
IN
OUT
1µF
1
FROM
OPTOISOLATED
INPUTS
2
3
CLK
8
6
VCC
VREF
DIN
VOUT
LTC1655
10k
4N28
5k
3
+
7
3k
2
–
6
1k
Q1
2N3440
4
RS
10Ω
5V
500Ω
75k
1%
LT®1077
5
CLK
DIN
CS/LD
20k
CS/LD
GND
OPTOISOLATORS
7
150k
1%
IOUT
CLK
DIN
CS/LD
1655/55L TA03
11
LTC1655/LTC1655L
U
TYPICAL APPLICATIONS
the onboard reference is always sourcing current and
never has to sink any current even when VOUT 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.
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
A Wide Swing, Bipolar Output 16-Bit DAC
5V
0.1µF
8
1
µP
2
3
VCC
CLK
DIN
CS/LD
VOUT
LTC1655
GND
VREF
5
6
R1
100k
1%
R2
200k
1%
TRANSFER CURVE
4.096
VOUT
– 4.096
12
0
32768
7
65535
R3
100k
1%
DIN
5V
3
+
7
LT1077
2
–
6
VOUT:
(2)(DIN)(4.096)
– 4.096V
65536
4
R4
– 5V 200k
1%
1655/55L TA05
R5
100k
1%
LTC1655/LTC1655L
U
TYPICAL APPLICATIONS
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 RA. If RA is
chosen to be 412Ω, the output current will range from
0mA at zero scale to 10mA at full scale. The minimum
voltage for VS is determined by the load resistor RL and
Q1’s VCESAT voltage. With a load resistor of 50Ω, the
voltage source can be 5V.
Digitally Programmable Current Source
5V
8
1
µP
2
3
5V < VS < 100V
FOR RL ≤ 50Ω
0.1µF
VCC
CLK
DIN
LTC1655
CS/LD
GND
5
VOUT
7
3
2
+
LT1218
–
RL
7
6
Q1
2N3440
(DIN)(4.096)
(65536)(RA)
≈ 0mA TO 10mA
IOUT =
4
RA
412Ω
1%
1655/55L TA04
13
LTC1655/LTC1655L
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
0.300 – 0.325
(7.620 – 8.255)
0.009 – 0.015
(0.229 – 0.381)
(
+0.035
0.325 –0.015
8.255
+0.889
–0.381
)
0.045 – 0.065
(1.143 – 1.651)
0.065
(1.651)
TYP
0.100
(2.54)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
14
0.130 ± 0.005
(3.302 ± 0.127)
0.125
(3.175) 0.020
MIN
(0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
N8 1098
LTC1655/LTC1655L
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*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
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SO8 1298
15
LTC1655/LTC1655L
U
TYPICAL APPLICATION
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
5V
0.1µF
8
1
µP
2
3
VCC
CLK
DIN
CS/LD
LTC1655/
LTC1655L
VOUT
7
R1
100k
GND
5
–5V
1655/55L TA06
RELATED PARTS
PART
NUMBER
DESCRIPTION
COMMENTS
LTC1257
Single 12-Bit VOUT DAC, Full Scale: 2.048V, VCC: 4.75V to 15.75V,
in Reference Can Be Overdriven Up to 12V, i.e., FSMAX = 12V
5V to 15V Single Supply, Complete VOUT DAC SO-8 Package
LTC1446/
LTC1446L
Dual 12-Bit VOUT DACs in SO-8 Package
LTC1446: VCC = 4.5V to 5.5V, VOUT = 0V to 4.095V
LTC1446L: VCC = 2.7V to 5.5V, VOUT = 0V to 2.5V
LTC1448
Dual 12-Bit VOUT DAC, VCC: 2.7V to 5.5V
Output Swings from GND to REF. REF Input Can Be Tied to VCC
LTC1450/
LTC1450L
Single 12-Bit VOUT DACs with Parallel Interface
LTC1450: VCC = 4.5V to 5.5V, VOUT = 0V to 4.095V
LTC1450L: VCC = 2.7V to 5.5V, VOUT = 0V to 2.5V
LTC1451
Single Rail-to-Rail 12-Bit DAC, Full Scale: 4.095V, VCC: 4.5V to 5.5V,
Internal 2.048V Reference Brought Out to Pin
5V, Low Power Complete VOUT DAC in SO-8 Package
LTC1452
Single Rail-to-Rail 12-Bit VOUT Multiplying DAC, VCC: 2.7V to 5.5V
Low Power, Multiplying VOUT DAC with Rail-to-Rail
Buffer Amplifier in SO-8 Package
LTC1453
Single Rail-to-Rail 12-Bit VOUT DAC, Full Scale: 2.5V, VCC: 2.7V to 5.5V 3V, Low Power, Complete VOUT DAC in SO-8 Package
LTC1454/
LTC1454L
Dual 12-Bit VOUT DACs in SO-16 Package with Added Functionality
LTC1454: VCC = 4.5V to 5.5V, VOUT = 0V to 4.095V
LTC1454L: VCC = 2.7V to 5.5V, VOUT = 0V to 2.5V
LTC1456
Single Rail-to-Rail Output 12-Bit DAC with Clear Pin,
Full Scale: 4.095V, VCC: 4.5V to 5.5V
Low Power, Complete VOUT DAC in SO-8
Package with Clear Pin
LTC1458/
LTC1458L
Quad 12 Bit Rail-to-Rail Output DACs with Added Functionality
LTC1458: VCC = 4.5V to 5.5V, VOUT = 0V to 4.095V
LTC1458L: VCC = 2.7V to 5.5V, VOUT = 0V to 2.5V
LTC1650
Single 16-Bit VOUT Industrial DAC in 16-Pin SO, VCC = ±5V
Low Power, Deglitched, 4-Quadrant Mulitplying VOUT DAC,
Output Swing ±4.5V
LTC1654
Dual 14-Bit DAC
1LSB DNL, 2 DACs in SO-8 Footprint
LTC1657/
LTC1657L
Single 16-Bit VOUT DAC with Parallel Interface
LTC1657: VCC = 5V, Low Power, Deglitched, VOUT = 0V to 4.096V
LTC1657L: VCC = 3V, Low Power, Deglitched, VOUT = 0V to 2.5V
LTC1658
Single Rail-to-Rail 14-Bit VOUT DAC in 8-Pin MSOP,
VCC = 2.7V to 5.5V
Low Power, Multiplying VOUT DAC in MS8 Package. Output
Swings from GND to REF. REF Input Can Be Tied to VCC
LTC1659
Single Rail-to-Rail 12-Bit VOUT DAC in 8-Pin MSOP,
VCC = 2.7V to 5.5V
Low Power, Multiplying VOUT DAC in MS8 Package. Output
Swings from GND to REF. REF Input Can Be Tied to VCC
16
Linear Technology Corporation
16555lf LT/TP 0800 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1998