Data Sheet

AD9748

Rev. B

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FEATURES

High performance member of pin-compatible

TxDAC product family

Linearity

0.1 LSB DNL

0.1 LSB INL

Twos complement or straight binary data format

Differential current outputs: 2 mA to 20 mA

Power dissipation: 135 mW @ 3.3 V

Power-down mode: 15 mW @ 3.3 V

On-chip 1.20 V reference

CMOS-compatible digital interface

32-lead LFCSP

Edge-triggered latches

Fast settling: 11 ns to 0.1% full-scale

APPLICATIONS

Communications

Direct digital synthesis (DSS)

Instrumentation

FUNCTIONAL BLOCK DIAGRAM

1.2V REF

3.3V

0.1

µF

CLK+

SLEEP

REFIO

FS ADJ

DVDD

DCOM

DIGITAL DATA INPUTS (DB7–DB0)

150pF

3.3V

AVDD

ACOM

AD9748

CURRENT

SOURCE

ARRAY

IOUTA

IOUTB

MODE

LSB

SWITCHES

SEGMENTED

SWITCHES

3.3V

CLKVDD

CLKCOM

CLK–

CMODE

LATCHES

Figure 1.

GENERAL DESCRIPTION

The AD97481 is an 8-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 AD9748 offers

exceptional ac and dc performance while supporting update

rates up to 210 MSPS.

The AD9748’s low power dissipation makes it well suited for

portable and low power applications. Its power dissipation can

be further reduced to 60 mW with a slight degradation in

performance by lowering the full-scale current output. In

addition, 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. 32-lead LFCSP.

2. The AD9748 is the 8-bit member of the pin-compatible

TxDAC family, which offers excellent INL and DNL

performance.

3. Differential or single-ended clock input (LVPECL or

CMOS), supports 210 MSPS conversion rate.

4. Data input supports twos complement or straight binary

data coding.

5. 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.

6. On-chip voltage reference: The AD9748 includes a 1.2 V

temperature-compensated band gap voltage reference.

1

Protected by U.S. Patent Numbers 5568145, 5689257, and 5703519.