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a

Dual Logarithmic D/A Converter

AD7112*

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

Tel: 617/329-4700

Fax: 617/326-8703

FUNCTIONAL BLOCK DIAGRAM

17-BIT DAC A

AD7112

OUT A

AGND

DGND

CS

WR

17-BIT LATCH

17

17-BIT LATCH

17-BIT DAC B

OUT B

DECODE LOGIC

DAC A/

DAC B

CONTROL

LOGIC

8-BIT

BUFFER

DB0

DB7

FEATURES

Dynamic Range: 88.5 dB

Resolution: 0.375 dB

On-Chip Data Latches for Both DACs

Four-Quadrant Multiplication

+5 V Operation

Pin Compatible with AD7528

Low Power

APPLICATIONS

Audio Attenuators

Sonar Systems

Function Generators

GENERAL DESCRIPTION

The LOGDAC® AD7112 is a monolithic dual multiplying D/A

converter featuring wide dynamic range and excellent DAC-to-

DAC matching. Both DACs can attenuate an analog input sig-

nal over the range 0 dB to 88.5 dB in 0.375 dB steps. It is

available in skinny 0.3" wide 20-pin DIPs and in 20-terminal

surface mount packages.

The degree of attenuation in either channel is determined by the

8-bit word applied to the onboard decode logic. This 8-bit word

is decoded into a 17-bit word which is then loaded into one of

the 17-bit data latches, determined by DACA/DACB. The fine

step resolution over the entire dynamic range is due to the use of

these 17-bit DACs.

The AD7112 is easily interfaced to a standard 8-bit MPU bus

via an 8-bit data port and standard microprocessor control lines.

It should be noted that the AD7112 is exactly pin-compatible

with the AD7528, an industry standard dual 8-bit multiplying

DAC. This allows an easy upgrading of existing AD7528 de-

signs which would benefit both from the wider dynamic range

and the finer step resolution offered by the AD7112.

The AD7112 is fabricated in Linear Compatible CMOS

bines precision bipolar circuits with low power CMOS logic.

*Protected by U.S. Patent No. 4521764.

LOGDAC is a registered trademark of Analog Devices, Inc.

PRODUCT HIGHLIGHTS

1. DAC-to-DAC Matching: Since both of the AD7112 DACs

are fabricated at the same time on the same chip, precise

matching and tracking between the two DACs is inherent.

2. Small Package: The AD7112 is available in a 20-pin DIP

and a 20-terminal SOIC package.

3. Fast Microprocessor Interface: The AD7112 has bus inter-

face timing compatible with all modern microprocessors.