REV. A

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a

Analog I/O Port

AD7769

FUNCTIONAL BLOCK DIAGRAM

PRODUCT HIGHLIGHTS

1. Two-Channel, 8-Bit Analog I/O port on a Single Chip.

The AD7769 contains a two-channel, high speed ADC with

input signal conditioning and two, fast settling 8-bit DACs

with output amplifiers, on a single chip.

2. Independent Control of Span and Offset.

The input voltage span of the ADC and the midpoint of the

transfer function, the output voltage swing of the two DACs

and the half-scale output voltage, can be set independently

by applying ground referenced control voltages.

3. Dynamic Specifications for DSP Users.

In addition to the traditional ADC and DAC specifications,

the AD7769 is specified with ac parameters including signal-

to-noise ratio, distortion and signal bandwidth.

4. Fast Microprocessor Interface.

The AD7769 has bus interface timing compatible with all

modern microprocessors, with bus access and relinquish

times less than 65 ns and a Write pulse width less than 90 ns.

FEATURES

Two-Channel, 8-Bit 2.5

s ADC

Two 8-Bit, 2.5

s DACs with Output Amplifiers

Span and Offset of ADC and DAC

Independently Adjustable

Low Power

APPLICATIONS

Winchester Disk Servo Controllers

Floppy Disk Microstepping

Closed Loop Servo Systems

GENERAL DESCRIPTION

The AD7769 is a complete, two-channel, 8-bit, analog I/O port.

It has versatile input and output signal conditioning features

that make it ideal for use in head-positioning servos in Winches-

ter disk systems. It is equally suitable for floppy disk microstep-

ping head positioning, other closed loop digital servo systems

and general purpose 8-bit data acquisition.

The AD7769 contains a high speed successive approximation

ADC, preceded by a two-channel multiplexer and signal condi-

tioning circuits. The input span of the ADC and the offset of

the zero point from ground can be independently set by apply-

ing ground referenced voltages. The AD7769 also contains two

independent, fast settling, 8-bit DACs with output amplifiers.

The output span and offset voltage of the DACs can be set inde-

pendently of those of the ADC. This makes the AD7769 espe-

cially useful in disk drives, where only a positive supply rail is

available and the ranges of the ADC and DACs must be refer-

enced to some positive voltage less than the supply.

The AD7769 is easily interfaced to a standard 8-bit mpu bus via

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

The AD7769 is fabricated in Linear Compatible CMOS

(LC

bines precision bipolar circuits with low power CMOS logic.

The part is available in a 28-lead plastic DIP and 28-terminal

PLCC package.

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.comFax:

617/326-8703

© Analog Devices, Inc., 1997