Operating Temperature Range *

0

°C to +70°C0°C to +70°C

18-Pin

18-Pin

Plastic Pin

Small Outline

Package

Package (SOIC)

ALD521DPD

ALD521DSD

FEATURES AND BENEFITS

• Low cost, simple functionality

• PC parallel printer port interface standard

• Support resolution up to 23 binary bits + sign

polarity bit

• Easy to use to acquire up to 23 bit linearity

and noise performance

• Integration time can be set by the user

• Easy user evaluation and setting of

conversion parameters

• Low power dissipation - 4 mA typical

including crystal oscillator

• On-chip Crystal Oscillator Circuit

• Two way asynchronous handshake data

transfer

• Conversion speed versus resolution trade-off

• Power down (sleep mode) control input to

power down to 2

µA

• Chip Select control input

when chip not selected

• Single 3 V to 5 V power supply

ALD521D

ORDERING INFORMATION

24 BIT SERIAL INTERFACE DIGITAL CONTROLLER

APPLICATIONS

• Operate in conjunction with ALD500/ALD500R

Precision analog signal processors

• High accuracy DC voltage measurement functions

• Portable battery operated instruments

• PC-based software control or stand-alone operation (without

other processors or PC)

• Serial digital output interface to other microprocessors or

microcontrollers

GENERAL DESCRIPTION

The ALD521D is a digital controller designed to interface to the ALD500

or ALD500R integrating dual slope analog processors as a chip set for

building a precision analog-to-digital converter. With the ALD521D and

ALD500R, together with a few external capacitors and resistors, a

precision Analog to Digital converter with auto zero and auto-polarity

can be implemented.

The ALD521D can operate in either a stand-alone mode or in an

external microprocessor control mode. In the stand-alone mode, the

ALD521D can either making continuous measurements or a single

measurement. Under external microprocessor control, the ALD521D

can directly interact with a PC under PC software control via a standard

parallel printer port with no other components, or it can also communicate

with other microcontrollers serially.

The ALD500/ALD500R analog processors consist of on-chip digital

control circuitry to accept control inputs, integrating buffer amplifiers,

analog switches, and voltage comparators. It functions in four operating

modes, or phases, namely auto zero, integrate, deintegrate, and

integrator zero phases. At the end of a conversion, the comparator

output goes from high to low when the integrator crosses zero during

deintegration.

ALD500 analog processors also provide direct logic

interface to CMOS logic families.

© 2000 Advanced Linear Devices, Inc., 415 Tasman Drive, Sunnyvale, California 94089-1706, Tel: (408) 747-1155, Fax: (408) 747-1286

http://www.aldinc.com

PIN CONFIGURATION

1

2

3

14

15

16

4

13

5

12

DGND

A

6

7

8

10

11

PWRUP

9

B

DV

PD, SD PACKAGE

17

18

V+

N/C

ALD521D

CS