Datasheet

ManualsBrandsLinear Technology ManualsDAC - Digital to AnalogD/A Converter IC 12bit SOIC-

LTC1446/LTC1446L

APPLICATIO S

DESCRIPTIO

FEATURES

TYPICAL APPLICATION

Dual 12-Bit Rail-to-Rail

Micropower DACs in SO-8

■

Dual DACs with 12-Bit Resolution

■

SO-8 Package

■

Rail-to-Rail Output Amplifiers

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Internal Reference

■

Maximum DNL Error: 0.5LSB

■

3V Operation (LTC1446L): I

= 650µA Typ

■

5V Operation (LTC1446): I

= 1000µA Typ

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Settling Time: 14µs to ±0.5LSB

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Power-On Reset Clears DACs to 0V

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3-Wire Cascadable Serial Interface with 500kHz

Update Rate

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Schmitt Trigger On Input Allows Direct

Optocoupler Interface

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Low Cost

The LTC

1446/LTC1446L are dual 12-bit digital-to-analog

converters (DACs) available in an SO-8 package. They are

complete with a rail-to-rail voltage

output amplifier, an

internal reference and an easy-to-use 3-wire cascadable

serial interface.

The LTC1446 has an internal reference and a full-scale

output of 4.095V. It operates from a single 4.5V to 5.5V

supply.

The LTC1446L has an internal reference and a full-scale

output of 2.5V. It operates from a single 2.7V to 5.5V

supply.

The low power supply current makes the LTC1446 family

ideal for battery-powered applications. These DACs are

available in space saving 8-pin SO and PDIP packages and

require no external components for operation.

Differential Nonlinearity vs Input Code

CODE

–0.5

DNL ERROR (LSB)

–0.4

–0.2

–0.1

0.5

0.2

1024 2048 2560

1446/46L G13

–0.3

0.3

0.4

0.1

512 1536 3072 3584 4095

–

12-BIT

DAC B

LTC1446: 5V

LTC1446L: 3V TO 5V

RAIL-TO-RAIL

VOLTAGE

OUTPUT

12-BIT

DAC A

POWER-ON

RESET

24-BIT

SHIFT

REG

AND

DAC

LATCH

µP

OUT

1446/1446L TA01

CLK1

CS/LD3

OUT B

OUT A

GND

Functional Block Diagram: Dual 12-Bit Rail-to-Rail DAC

■

Digital Calibration

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Industrial Process Control

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Automatic Test Equipment

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Cellular Telephones

, LTC and LT are registered trademarks of Linear Technology Corporation.

Summary of content (12 pages)

PAGE 1
LTC1446/LTC1446L Dual 12-Bit Rail-to-Rail Micropower DACs in SO-8 U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Dual DACs with 12-Bit Resolution SO-8 Package Rail-to-Rail Output Amplifiers Internal Reference Maximum DNL Error: 0.5LSB 3V Operation (LTC1446L): ICC = 650µA Typ 5V Operation (LTC1446): ICC = 1000µA Typ Settling Time: 14µs to ±0.
PAGE 2
LTC1446/LTC1446L W W W AXI U U ABSOLUTE RATI GS (Note 1) VCC to GND ................................................ –0.5 to 7.5V Logic Inputs to GND ................................... –0.5 to 7.5V Operating Temperature Range LTC1446C/LTC1446LC ............................ 0°C to 70°C LTC1446I/LTC1446LI ..........................–40°C to 85°C VOUT A /VOUT B ................................. –0.5V to VCC + 0.5V Maximum Junction Temperature .......................... 125°C Storage Temperature Range ..
PAGE 3
LTC1446/LTC1446L ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range. VCC = 4.5V to 5.5V (LTC1446), 2.7V to 5.5V (LTC1446L), VOUT A and VOUT B unloaded, TA = TMIN to TMAX, unless otherwise noted.
PAGE 4
LTC1446/LTC1446L U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1446 Differential Nonlinearity (DNL) LTC1446 Integral Nonlinearity (INL) 0.5 LTC1446L Differential Nonlinearity 0.5 3 0.4 0.4 2 0.1 0 –0.1 –0.2 –0.3 0.3 DNL ERROR (LSB) 0.2 INL ERROR (LSB) DNL ERROR (LSB) 0.3 1 0 –1 0.2 0.1 0 –0.1 –0.2 –0.3 –2 –0.4 –0.4 –0.5 0 –0.
PAGE 5
LTC1446/LTC1446L U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1446 Supply Current vs Temperature LTC1446L Supply Current vs Temperature 970 700 1.1 960 690 1.0 0.9 0.8 0.7 0.6 0.5 0.5 950 VCC = 5.5V 940 930 VCC = 5V 920 910 1.0 1.5 2.0 2.5 3.0 SUPPLY CURRENT (µA) 1.2 SUPPLY CURRENT (µA) SUPPLY CURRENT (mA) LTC1446L Supply Current vs Logic Input Voltage LOGIC INPUT VOLTAGE (V) 5 25 45 65 85 105 125 TEMPERATURE (°C) 1446/46L G10 VCC = 3.3V 670 660 VCC = 3V 650 640 VCC = 2.
PAGE 6
LTC1446/LTC1446L W BLOCK DIAGRAM REFERENCE 12-BIT DAC B LD CLK 1 + DAC B REGISTER 24-BIT SHIFT REGISTER DIN 2 LD CS/LD 3 8 VOUT B 7 VCC 6 GND 5 VOUT A – DAC A REGISTER 12-BIT DAC A + DOUT 4 – POWER-ON RESET 1446BD WU W TI I G DIAGRA t4 t3 t1 t2 t6 t7 CLK t9 DIN B0-B PREVIOUS WORD B11-A MSB B0-A LSB B11-B MSB B0-B LSB t5 t8 CS/LD DOUT B11-A PREVIOUS WORD B10-A PREVIOUS WORD B0-A PREVIOUS WORD B11-B PREV WORD B10-B PREV WORD B0-B PREV WORD B11-A CURRENT WORD 1446
PAGE 7
LTC1446/LTC1446L U U DEFI ITIO S Nominal LSBs: Resolution (n) Resolution is defined as the number of digital input bits, n. It defines the number of DAC output states (2n) that divide the full-scale range. The resolution does not imply linearity. LTC1446 LSB = 4.095V/4095 = 1mV LTC1446L LSB = 2.5V/4095 = 0.610mV Zero Scale Error (ZSE) This is the output of the DAC when all bits are set to one. The output voltage when the DAC is loaded with all zeros.
PAGE 8
LTC1446/LTC1446L U OPERATIO Serial Interface Voltage Output The data on the DIN input is loaded into the shift register on the rising edge of the clock. Data is loaded as one 24bit word where the first 12 bits are for DAC A and the second 12 are for DAC B. For each 12-bit segment the MSB is loaded first. Data from the shift register is loaded into the DAC register when CS/LD is pulled high. The clock is disabled internally when CS/LD is high.
PAGE 9
LTC1446/LTC1446L U TYPICAL APPLICATIONS N This circuit shows how to use an LTC1446 and an LT ®1077 to make a wide bipolar output swing 12-bit DAC with an offset that can be digitally programmed. VOUT A, which can be set by loading the appropriate digital code for DAC A, sets the offset. As this value changes, the transfer curve for the output moves up and down as illustrated in the graph below. A Wide Swing, Bipolar Output DAC with Digitally Controlled Offset 5V 0.
PAGE 10
LTC1446/LTC1446L U TYPICAL APPLICATIONS N the REF + pin on the LTC1296. The LTC1296 has a Shutdown pin that goes low in shutdown mode. This will turn off the PNP transistor supplying power to the LTC1446. The resistor and capacitor on the LTC1446 outputs act as a lowpass filter for noise. This circuit shows how to use one LTC1446 to make an autoranging ADC. The microprocessor sets the reference span and the Common pin for the analog input by loading the appropriate digital code into the LTC1446.
PAGE 11
LTC1446/LTC1446L 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) 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) ( 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 0.125 (3.175) MIN 0.005 (0.127) MIN +0.025 0.325 –0.015 +0.635 8.255 –0.381 ) 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.
PAGE 12
LTC1446/LTC1446L RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1257 Single 12-Bit VOUT DAC, Full Scale: 2.048V, VCC: 4.75V to 15.75V, 5V to 15V Single Supply, Complete VOUT DAC in SO-8 Package Reference Can Be Overdriven up to 12V, i.e., FS Max = 12V LTC1451 Single Rail-to-Rail Output 12-Bit DAC, Full Scale: 4.095V, VCC: 4.5V to 5.5V Internal 2.048V Reference Brought Out to Pin LTC1452 Single Rail-to-Rail 12-Bit VOUT Mulitplying DAC, VCC: 2.7V to 5.