LTC1257
Complete Single Supply
12-Bit Voltage Output
DAC in SO-8
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
8-Pin SO Package
Buffered Voltage Output
Built-In 2.048V Reference
500µV/LSB with 2.048V Full Scale
1/2LSB Max DNL Error
Guaranteed 12-Bit Monotonic
3-Wire Cascadable Serial Interface
Wide Single Supply Range: V
CC
= 4.75V to 15.75V
Low Power: I
CC
Typ = 350µA with 5V Supply
APPLICATIO S
s
s
s
The LTC
®
1257 is a complete single supply, 12-bit voltage
output D/A converter (DAC) in an SO-8 package. The
LTC1257 includes an output buffer amplifier, 2.048V
voltage reference and an easy to use three-wire cascadable
serial interface. An external reference can be used to
override the internal reference and extend the output
voltage range to 12V. The power supply current is a low
350µA when operating from a 5V supply, making the
LTC1257 ideal for battery-powered applications. The space-
saving 8-pin SO package and operation with no external
components provide the smallest 12-bit D/A system
available.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Digital Offset/Gain Adjustment
Industrial Process Control
Automatic Test Equipment
TYPICAL APPLICATIO
Daisy-Chained Control Outputs
5V
0.5
Differential Nonlinearity
vs Input Code
V
CC
V
OUT
LTC1257
GND V
REF
D
IN
CLK
LOAD
D
OUT
µP
DNL ERROR (LSBs)
0.1µF
CONTROL OUTPUT 1
0.0
0.1µF
CONTROL OUTPUT 2
V
CC
V
OUT
LTC1257
GND V
REF
D
IN
CLK
LOAD
D
OUT
–0.5
TO NEXT DAC
1257 TA01
0
512 1024 1536 2048 2560 3072 3584 4098
CODE
1257 TA05
U
U
U
1
LTC1257
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
CLK 1
D
IN
2
LOAD 3
D
OUT
4
N8 PACKAGE
8-LEAD PDIP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
TOP VIEW
CLK 1
D
IN
2
LOAD 3
D
OUT
4
8 V
CC
7 V
OUT
6 REF
5 GND
8 V
CC
7 V
OUT
6 REF
5 GND
V
CC
to GND ............................................ – 0.5V to 16.5V
TTL Input Voltage .......................... – 0.5V to V
CC
+ 0.5V
V
OUT
.............................................. – 0.5V to V
CC
+ 0.5V
REF ................................................ – 0.5V to V
CC
+ 0.5V
Operating Temperature Range
LTC1257C ............................................. 0°C to 70°C
LTC1257I ........................................ – 40°C to 85°C
Maximum Junction Temperature
Plastic Package ............................. – 65°C to 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1257CN8
LTC1257IN8
LTC1257CS8
LTC1257IS8
S8 PART MARKING
1257
1257I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 150°C/W
Consult LTC Marketing for parts specified with wider operating temperature
ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
T
A
= T
MIN
to T
MAX
. V
CC
= 4.75V to 15.75V, internal or external reference (2.475V
≤
V
REF
≤
V
CC
– 2.7V), unless otherwise noted.
SYMBOL
DAC
DNL
INL
OFF
PARAMETER
Resolution
Differential Nonlinearity
Integral Nonlinearity
Offset Error
CONDITIONS
q
MIN
12
TYP
MAX
UNITS
Bits
LSB
LSB
LSB
LSB
LSB
mV
mV
LSB/°C
µV/°C
LSB
LSB/°C
V
V
LSB/°C
LSB/ V
LSB/V
LSB
V
kΩ
pF
mA
OFF
TC
Offset Error Tempco
Gain Error
Gain Error Tempco
Guaranteed Monotonic (Note 4)
LTC1257C (Note 4)
LTC1257I (Note 4)
When Using Internal Reference, LTC1257C
When Using Internal Reference, LTC1257I
When Using External Reference, LTC1257C
When Using External Reference, LTC1257I
When Using Internal Reference (Note 2)
When Using External Reference (Note 2)
(Note 2)
I
REF
= 0, LTC1257C
I
REF
= 0, LTC1257I
I
REF
= 0
I
REF
= 0, LTC1257C
I
REF
= 0, LTC1257I
0
≤
I
REF
≤
100µA
V
CC
> V
REF
+ 2.7V
(Note 2)
V
REF
Shorted to GND
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
±0.02
±15
0.5
±
0.01
2.028
2.018
2.048
±0.06
±0.5
±3.5
±4.0
±8
±10
±4
±5
±0.066
±30
±2
±0.02
2.068
2.078
±0.4
±0.7
±1
12
18
90
Reference
Reference Output Voltage
Reference Output Tempco
Reference Line Regulation
Reference Load Regulation
Reference Input Range
Reference Input Resistance
Reference Input Capacitance
Short-Circuit Current
2.475
8
14
15
2
U
W
U
U
W W
W
LTC1257
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
T
A
= T
MIN
to T
MAX
. V
CC
= 4.75V to 15.75V, internal or external reference (2.475V
≤
V
REF
≤
V
CC
– 2.7V), unless otherwise noted.
SYMBOL
V
CC
I
CC
PARAMETER
Positive Supply Voltage
Supply Current
CONDITIONS
For Specified Performance
4.75V
≤
V
CC
≤
5.25V
4.75V
≤
V
CC
≤
15.75V
V
OUT
Shorted to GND
V
OUT
Shorted to V
CC
Input Code = 0
5kΩ in Parallel with 100pF
To
±1/2LSB,
5kΩ in Parallel with 100pF, V
CC
= 4.75V
(Notes 2,3)
q
q
q
q
q
MIN
4.75
TYP
MAX
15.75
UNITS
V
µA
µA
mA
mA
Ω
V/µs
Power Supply
350
800
600
1500
60
60
250
1.0
6
50
2.4
0.8
V
CC
– 1
0.4
±10
10
100
25
350
350
150
0
0
35
150
1.4
Note 3:
DAC switched from all 1s to all 0s, and all 0s to all 1s code.
Note 4:
Guaranteed with internal V
REF
or with external V
REF
range of
2.475V to 12V. Tested at 10V.
500
Op Amp DC Performance
Short-Circuit Current Low
Short-Circuit Current High
Output Impedance to GND
AC Performance
Voltage Output Slew Rate
Voltage Output Settling Time
Digital Feedthrough
Digital I/O
V
IH
V
IL
V
OH
V
OL
I
LEAK
C
IN
t1
t2
t3
t4
t5
t6
t7
t8
f
CLK
Digital Input High Voltage
Digital Input Low Voltage
Digital Output High Voltage
Digital Output Low Voltage
Digital Input Leakage
Digital Input Capacitance
D
IN
Valid to CLK Setup
D
IN
Valid to CLK Hold
CLK High Time
CLK Low Time
LOAD Pulse Width
LSB CLK to LOAD
LOAD High to CLK
D
OUT
Output Delay
Maximum Clock Frequency
C
LOAD
= 15pF
I
OUT
= –1mA, D
OUT
Only
I
OUT
= 1mA, D
OUT
Only
V
IN
= GND to V
CC
(Note 2)
V
V
V
V
µA
pF
ns
ns
ns
ns
ns
ns
ns
ns
MHz
q
q
q
q
q
µs
nV/s
q
q
q
q
Switching (Note 2)
q
q
q
q
q
q
q
q
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Guaranteed by design; not subject to test.
3
LTC1257
TYPICAL PERFOR A CE CHARACTERISTICS
Minimum Supply Voltage
vs Load Current #1
5.0
4.8
MINIMUM SUPPLY VOLTAGE (V)
MINIMUM SUPPLY VOLTAGE (V)
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
0.01
SUPPLY CURRENT (mA)
V
REF
= INTERNAL
V
OUT
= FULL SCALE
T
A
= 25°C
0.1
1
OUTPUT LOAD CURRENT (mA)
Supply Current vs
Logic Input Voltage
0.59
V
CC
= 5V
T
A
= 25°C
OUTPUT VOLTAGE SWING (V)
0.54
SUPPLY CURRENT (mA)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
FULL SCALE
R
L
TIED TO GND
ZERO SCALE
R
L
TIED TO V
CC
OUTPUT PULL-DOWN VOLTAGE (mV)
0.49
0.44
0.39
0.34
0
1
3
2
LOGIC VOLTAGE (V)
4
5
1257 G04
Full-Scale Voltage vs
Temperature
2.0495
2.0490
FULL-SCALE VOLTAGE (V)
0.9
V
CC
= 5V
INTERNAL REFERENCE
ZERO-SCALE VOLTAGE (mV)
ERROR (LSB)
2.0485
2.0480
2.0475
2.0470
2.0465
–50 –25
50
25
75
0
TEMPERATURE (°C)
4
U W
100
Minimum Supply Voltage
vs Load Current #2
15.0
14.5
14.0
13.5
13.0
12.5
12.0
11.5
11.0
0.01
0.1
1
OUTPUT LOAD CURRENT (mA)
10
1257 G02
Supply Current vs Temperature
0.38
0.37
0.36
0.35
0.34
V
CC
= 4.75V
0.33
0.32
0.31
–50 –25
V
CC
= 5V
V
REF
= 10V
V
OUT
= FULL SCALE
T
A
= 25°C
V
CC
= 5.25V
10
1257 G01
50
25
75
0
TEMPERATURE (°C)
100
125
1257 G03
Output Swing vs Load Resistance
5.0
4.5
V
CC
= 5V
1000
Pull-Down Voltage vs Output Sink
Current Capability
100
10
HOT
COLD
1
ROOM
0
10
0.1
100
1k
LOAD RESISTANCE (Ω)
10k
1257 G05
1
10
100
OUTPUT SINK CURRENT (µA)
1000
1257 G06
Zero-Scale Voltage vs
Temperature
2.0
V
CC
= 5V
INTERNAL REFERENCE
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Integral Nonlinearity (INL)
1.6
1.2
0.8
0.4
0
–0.4
–0.8
–1.2
–1.6
–2.0
V
CC
= 5V
INTERNAL REFERENCE
T
A
= 25°C
0
512 1024 1536 2048 2560 3072 3584 4096
CODE
1257 G09
125
0
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
1257 G07
1257 G08
LTC1257
TYPICAL PERFOR A CE CHARACTERISTICS
Differential Nonlinearity (DNL)
REFERENCE COMPENSATION RESISTANCE (Ω)
0.5
DNL ERROR (LSBs)
0.0
30
20
10
0
0.01
–0.5
0
512 1024 1536 2048 2560 3072 3584 4098
CODE
1257 TA05
0.1
1
C
L
(µF)
10
100
1257 G11
0.1V/DIV
PI FU CTIO S
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.
LOAD (Pin 3):
The TTL level input for the serial interface
load control. Data is loaded from the shift register into the
DAC register, thus updating the DAC output when LOAD is
pulled low. The DAC register is transparent as long as
LOAD is held low.
D
OUT
(Pin 4):
The output of the shift register which
becomes valid on the rising edge of the serial clock. The
D
OUT
pin is driven from GND to V
CC
by an internal CMOS
inverter. Multiple LTC1257s may be cascaded by connect-
ing the D
OUT
pin to the D
IN
pin of the next chip.
GND (Pin 5):
Ground.
REF (Pin 6):
The output of the 2.048V reference and the
input to the DAC resistor ladder. An external reference with
voltage from 2.475V to V
CC
– 2.7V may be used to override
the internal reference.
V
OUT
(Pin 7):
The buffered DAC output is capable of
sourcing 2mA over temperature while pulling within 2.7V
of V
CC
. The output will pull to ground through an internal
250Ω equivalent resistance.
V
CC
(Pin 8):
The positive supply input. 4.75V
≤
V
CC
≤
15.75V. Requires a bypass capacitor to ground.
U W
Reference Compensation
Resistance vs C
L
70
60
50
40
Broadband Noise
CODE = FFF
H
BW = 3Hz TO 1MHz
GAIN = 1100×
TIME = 5ms/DIV
1257 G12
U
U
U
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
