Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsData collecting ICsData acquisition IC - DA converter (DAC) SOIC 8

LTC1257

1257fc

TYPICAL APPLICATION

FEATURES DESCRIPTION

Complete Single Supply

12-Bit Voltage Output

DAC in SO-8

The LT C

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 volt-

age reference and an easy to use 3-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.

Daisy-Chained Control Outputs Differential Nonlinearity

vs Input Code

APPLICATIONS

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

= 4.75V to 15.75V

Low Power: I

Typ = 350µA with 5V Supply

Digital Offset/Gain Adjustment

Industrial Process Control

Automatic Test Equipment

L, LT , LT C , LT M , Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

µP

0.1µF

CONTROL OUTPUT 1

CONTROL OUTPUT 2

REF

GND

OUT

CLK

LOAD

OUT

LTC1257

REF

GND

OUT

CLK

LOAD

OUT

LTC1257

TO NEXT DAC

1257 TA01

CODE

DNL ERROR (LSBs)

0.5

0.0

–0.5

1024 2048 2560

1257 TA05

512 1536 3072 3584

4098

Summary of content (12 pages)

PAGE 1
LTC1257 Complete Single Supply 12-Bit Voltage Output DAC in SO-8 FEATURES n n n n n n n n n DESCRIPTION 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: VCC = 4.75V to 15.75V Low Power: ICC Typ = 350µA with 5V Supply APPLICATIONS n n n The LTC®1257 is a complete single supply, 12-bit voltage output D/A converter (DAC) in an SO-8 package.
PAGE 2
LTC1257 ABSOLUTE MAXIMUM RATINGS (Note 1) VCC to GND.............................................. –0.5V to 16.5V TTL Input Voltage ........................... –0.5V to VCC + 0.5V VOUT................................................. –0.5V to VCC + 0.5V REF.................................................. –0.5V to VCC + 0.5V Operating Temperature Range LTC1257C................................................. 0°C to 70°C LTC1257I..............................................
PAGE 3
LTC1257 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = TMIN to TMAX. VCC = 4.75V to 15.75V, internal or external reference (2.475V ≤ VREF ≤ VCC – 2.7V), unless otherwise noted.
PAGE 4
LTC1257 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = TMIN to TMAX. VCC = 4.75V to 15.75V, internal or external reference (2.475V ≤ VREF ≤ VCC – 2.7V), unless otherwise noted. SYMBOL t5 t6 t7 t8 fCLK PARAMETER LOAD Pulse Width LSB CLK to LOAD LOAD High to CLK DOUT Output Delay Maximum Clock Frequency CONDITIONS MIN 150 0 0 35 l l l CLOAD = 15pF l TYP MAX UNITS ns ns ns ns MHz 150 1.
PAGE 5
LTC1257 TYPICAL PERFORMANCE CHARACTERISTICS Full-Scale Voltage vs Temperature Zero-Scale Voltage vs Temperature 2.0495 VCC = 5V INTERNAL REFERENCE 2.0480 2.0475 2.0470 50 25 75 0 TEMPERATURE (°C) 100 1.2 0.7 0.8 0.6 0.5 0.4 0.3 –1.2 –1.6 –25 0 25 50 75 TEMPERATURE (°C) 0 512 1024 1536 2048 2560 3072 3584 4098 CODE 100 125 –2.
PAGE 6
LTC1257 PIN FUNCTIONS VOUT (Pin 7): The buffered DAC output is capable of sourcing 2mA over temperature while pulling within 2.7V of VCC. The output will pull to ground through an internal 250Ω equivalent resistance. VCC (Pin 8): The positive supply input. 4.75V ≤ VCC ≤ 15.75V. Requires a bypass capacitor to ground. DEFINITIONS LSB: The least significant bit or the ideal voltage difference between two successive codes.
PAGE 7
LTC1257 BLOCK DIAGRAM LOGIC SUPPLY CLK DIN 5V REGULATOR VCC 12-BIT SHIFT REGISTER DOUT 12 LOAD GND 12-BIT LATCH 12 REF 2.
PAGE 8
LTC1257 OPERATION Serial Interface Reference The data on the DIN input is loaded into the shift register on the rising edge of the clock. The MSB is loaded first and the LSB last. The DAC register loads the data from the shift register when LOAD is pulled low, and remains transparent until LOAD is pulled high and the data is latched. The LTC1257 includes an internal 2.048V reference, making 1LSB equal to 500µV.
PAGE 9
LTC1257 TYPICAL APPLICATIONS Auto Ranging 8-Channel ADC with Shutdown 22µF 5V VCC CH0 8 ANALOG INPUT CHANNELS CS DOUT • • • LTC1296 DIN CH7 COM REF + REF – SSO 50k 50k 5V µP CLK 74HC04 0.1µF VCC 100Ω VOUT LTC1257 0.1µF 100Ω VOUT LTC1257 GND VREF LOAD DOUT GND VREF VCC 0.
PAGE 10
LTC1257 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. N Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510 Rev I) .300 – .325 (7.620 – 8.255) ( +.035 .325 –.015 8.255 +0.889 –0.381 .130 ±.005 (3.302 ±0.127) .045 – .065 (1.143 – 1.651) .065 (1.651) TYP .008 – .015 (0.203 – 0.381) ) .400* (10.160) MAX 8 7 6 1 2 3 5 .255 ±.015* (6.477 ±0.381) .120 (3.048) .020 MIN (0.508) MIN .018 ±.003 .100 (2.
PAGE 11
LTC1257 REVISION HISTORY (Revision history begins at Rev C) REV DATE DESCRIPTION C 12/12 Removed MAX Voltage Output Settling Time value in Electrical Characteristics section PAGE NUMBER 3 1257fc 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.
PAGE 12
LTC1257 TYPICAL APPLICATION Driving LTC1257 with Opto-Isolators 12V 2k 5% MOC5008 CLK 1 1 VOUT LOAD LTC1257 VOUT GND 6 4 2 5 MOC5008 LOAD VREF DIN DOUT 0.1µF 5 MOC5008 DIN CLK VCC 6 4 2 LT1021-5 VOUT VIN 2k 5% 2k 5% 1 6 4 1257 TA07 2 5 RELATED PARTS PART NUMBER DESCRIPTION 12 Bit LTC1446/LTC1446L Dual 12-Bit VOUT DACs in SO-8 Package LTC1448 Dual 12-Bit VOUT DAC in SO-8 Package, VCC: 2.7V to 5.