REV. 0

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

AD7870A

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

Tel: 617/329-4700

World Wide Web Site: http://www.analog.com

Fax: 617/326-8703

© Analog Devices, Inc., 1997

Complete, 12-Bit, 100 kHz , Sampling ADC

FUNCTIONAL BLOCK DIAGRAM

FEATURES

Complete Monolithic 12-Bit ADC with:

2

s Track/Hold Amplifier

8

s A/D Converter

On-Chip Reference

Laser-Trimmed Clock

Parallel, Byte and Serial Digital Interface

70 dB SNR at 10 kHz Input Frequency

57 ns Data Access Time

Low Power—60 mW typ

APPLICATIONS

Digital Signal Processing

Speech Recognition and Synthesis

Spectrum Analysis

High Speed Modems

DSP Servo Control

GENERAL DESCRIPTION

The AD7870A is a fast, complete, 12-bit A/D converter. It con-

sists of a track/hold amplifier, 8

µs successive approximation

ADC, 3 V buried Zener reference and versatile interface logic.

The ADC features a self-contained internal clock that is laser

trimmed to guarantee accurate control of conversion time. No

external clock timing components are required; the on-chip

clock may be overridden by an external clock if required.

AD7870A offers a choice of three data output formats: a single,

parallel, 12-bit word, two 8-bit bytes or serial data. Fast bus

access times and standard control inputs ensure easy interfacing

to modern microprocessors and digital signal processors.

The AD7870A operates from

± 5 V power supplies, accepts

bipolar input signals of

±3 V and can convert full power signals

up to 50 kHz.

In addition to the traditional dc accuracy specifications such as

linearity, full-scale and offset errors, the AD7870A is also fully

specified for dynamic performance parameters including har-

monic distortion and signal-to-noise ratio.

The AD7870A is fabricated in Analog Devices’ linear compati-

combines precision bipolar circuits with low power CMOS logic.

The part is available in a 24-pin, 0.3-inch wide, plastic dual in-

line package (DIP).

PRODUCT HIGHLIGHTS

1. Complete 12-bit ADC on a chip.

The AD7870A is the most complete monolithic ADC avail-

able and combines a 12-bit ADC with internal clock, track/

hold amplifier and reference on a single chip.

2. Dynamic specifications for DSP users.

The AD7870A is fully specified and tested for ac parameters,

including signal-to-noise ratio, harmonic distortion and inter-

modulation distortion. Key digital timing parameters are also

tested and guaranteed over the full operating temperature

range.

3. Fast microprocessor interface.

Data access times of 57 ns make the AD7870A compatible

with modern 8- and 16-bit microprocessors and digital signal

processors.