12-Bit, 210 MSPS

TxDAC Digital-to-Analog Converter

Data Sheet

AD9742

Rev. C

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FEATURES

High performance member of pin-compatible TxDAC

product family

Excellent spurious-free dynamic range performance

SNR at 5 MHz output, 125 MSPS: 70 dB

Twos complement or straight binary data format

Differential current outputs: 2 mA to 20 mA

Power dissipation: 135 mW at 3.3 V

Power-down mode: 15 mW at 3.3 V

On-chip 1.2 V Reference

CMOS compatible digital interface

28-lead SOIC, 28-lead TSSOP, and 32-lead LFCSP

Edge-triggered latches

APPLICATIONS

Wideband communication transmit channel:

Direct IF

Base stations

Wireless local loops

Digital radio links

Direct digital synthesis (DDS)

Instrumentation

FUNCTIONAL BLOCK DIAGRAM

1.2V REF

REFLO

3.3V

0.1

µF

CLOCK

SLEEP

REFIO

FS ADJ

DVDD

DCOM

CLOCK

DIGITAL DATA INPUTS (DB11–DB0)

150pF

3.3V

AVDD

ACOM

AD9742

CURRENT

SOURCE

ARRAY

IOUTA

IOUTB

MODE

LSB

SWITCHES

SEGMENTED

SWITCHES

LATCHES

Figure 1.

GENERAL DESCRIPTION

The AD97421 is a 12-bit resolution, wideband, third generation

member of the TxDAC series of high performance, low power

CMOS digital-to-analog converters (DACs). The TxDAC family,

consisting of pin-compatible 8-, 10-, 12-, and 14-bit DACs,

is specifically optimized for the transmit signal path of

communication systems. All of the devices share the same interface

options, small outline package, and pinout, providing an upward

or downward component selection path based on performance,

resolution, and cost. The AD9742 offers exceptional ac and dc

performance while supporting update rates up to 210 MSPS.

The AD9742’s low power dissipation makes it well suited for

portable and low power applications. Its power dissipation can

be further reduced to a mere 60 mW with a slight degradation

in performance by lowering the full-scale current output. Also,

a power-down mode reduces the standby power dissipation to

approximately 15 mW. A segmented current source architecture

is combined with a proprietary switching technique to reduce

spurious components and enhance dynamic performance.

Edge-triggered input latches and a 1.2 V temperature compensated

band gap reference have been integrated to provide a complete

monolithic DAC solution. The digital inputs support 3 V CMOS

logic families.

PRODUCT HIGHLIGHTS

1. The AD9742 is the 12-bit member of the pin-compatible

TxDAC family, which offers excellent INL and DNL

performance.

2. Data input supports twos complement or straight binary

data coding.

3. High speed, single-ended CMOS clock input supports

210 MSPS conversion rate.

4. Low power: Complete CMOS DAC function operates on

135 mW from a 2.7 V to 3.6 V single supply. The DAC full-

scale current can be reduced for lower power operation,

and a sleep mode is provided for low power idle periods.

5. On-chip voltage reference: The AD9742 includes a 1.2 V

temperature compensated band gap voltage reference.

6. Industry-standard 28-lead SOIC, 28-lead TSSOP, and

32-lead LFCSP packages.

1

Protected by U.S. Patent Numbers: 5,568,145; 5,689,257; and 5,703,519.