FUNCTIONAL BLOCK DIAGRAM

(MSB)

DB15

DB0

(LSB)

CLOCK

NC

REFCOM REFOUT

IREFIN

NR

LADCOM

IOUTB

IOUTA

DCOM

MSBs: SEGMENTED

CURRENT SOURCES

AND SWITCHES

MSB

DECODER

AND

EDGE-

TRIGGERED

BIT

LATCHES

LSBs:

CURRENT SOURCES,

SWITCHES, AND

1k

Ω R-2R

LADDERS

AD768

CONTROL

AMP

2.5V

BANDGAP

REFERENCE

1k

1k

REV. B

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

FEATURES

30 MSPS Update Rate

16-Bit Resolution

Linearity: 1/2 LSB DNL @ 14 Bits

1 LSB INL @ 14 Bits

Fast Settling: 25 ns Full-Scale Settling to 0.025%

SFDR @ 1 MHz Output: 86 dBc

THD @ 1 MHz Output: 71 dBc

Low Glitch Impulse: 35 pV-s

Power Dissipation: 465 mW

On-Chip 2.5 V Reference

Edge-Triggered Latches

Multiplying Reference Capability

APPLICATIONS

Arbitrary Waveform Generation

Communications Waveform Reconstruction

Vector Stroke Display

16-Bit, 30 MSPS

D/A Converter

AD768

PRODUCT DESCRIPTION

The AD768 is a 16-bit, high speed digital-to-analog converter

(DAC) that offers exceptional ac and dc performance. The

AD768 is manufactured on ADI’s Advanced Bipolar CMOS

(ABCMOS) process, combining the speed of bipolar transistors,

the accuracy of laser-trimmable thin film resistors, and the effi-

ciency of CMOS logic. A segmented current source architecture

is combined with a proprietary switching technique to reduce

glitch energy and maximize dynamic accuracy. Edge triggered

input latches and a temperature compensated bandgap reference

have been integrated to provide a complete monolithic DAC

solution.

The AD768 is a current-output DAC with a nominal full-scale

output current of 20 mA and a 1 k

Ω output impedance. Differ-

ential current outputs are provided to support single-ended

or differential applications. The current outputs may be tied

directly to an output resistor to provide a voltage output, or fed

to the summing junction of a high speed amplifier to provide a

buffered voltage output. Also, the differential outputs may be

interfaced to a transformer or differential amplifier.

The on-chip reference and control amplifier are configured for

maximum accuracy and flexibility. The AD768 can be driven by

the on-chip reference or by a variety of external reference volt-

ages based on the selection of an external resistor. An external

capacitor allows the user to optimally trade off reference band-

width and noise performance.

The AD768 operates on

±5 V supplies, typically consuming

465 mW of power. The AD768 is available in a 28-pin SOIC

package and is specified for operation over the industrial tem-

perature range.

PRODUCT HIGHLIGHTS

1. The low glitch and fast settling time provide outstanding

dynamic performance for waveform reconstruction or digital

synthesis requirements, including communications.

2. The excellent dc accuracy of the AD768 makes it suitable for

high speed A/D conversion applications.

3. On-chip, edge-triggered input CMOS latches interface

readily to CMOS logic families. The AD768 can support up-

date rates up to 40 MSPS.

4. A temperature compensated, 2.5 V bandgap reference is

included on-chip allowing for generation of the reference

input current with the use of a single external resistor. An ex-

ternal reference may also be used.

5. The current output(s) of the AD768 may be used singly or

differentially, either into a load resistor, external op amp

summing junction or transformer.

6. Proper selection of an external resistor and compensation

capacitor allow the performance-conscious user to optimize

the AD768 reference level and bandwidth for the target

application.

© Analog Devices, Inc., 1996

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703