MP3274

1

Rev. 4.00

Fault Protected 32 Channel, 12-Bit

Data Acquisition Subsystem

FEATURES

• Complete 32-Channel 12-Bit A/D Converter

with Sample & Hold, Reference, Clock and

3-State Outputs

• Fast Conversion, less than 15µS

• Microprocessor Bus Interface

• Parallel or Serial Data Output Modes

• 65 ns Bus Access Time

• Remote Analog Ground Sensing

• Overvoltage Protected Input (50 V over the

Supply Voltages)

• Precision Reference for Long Term Stability and

Low Gain T.C.

• Guaranteed Linearity Over Temperature

• Guaranteed Performance at +12/–5 V, ±12 & ±15 V

• Low Power (3 mW per Channel Typical)

• 16 Channel Version: MP3276 & MP3275

GENERAL DESCRIPTION

The MP3274 is a complete 32-channel, 12-bit Data Acquisi-

tion Subsystem with 3-state output buffers for direct interfacing

to 16-bit microprocessor buses. Implemented using an ad-

vanced BiCMOS process, the converter combines a 32-channel

passive overvoltage protected multiplexer instrumentation amp,

a sample & hold, a SAR, a 12-bit decoded D/A, a comparator, a

precision reference and the control logic to achieve an accurate,

repeated conversion in less than 15

µs, and a mux/instrumenta-

tion amp settling period of less than 10

µs.

A unique input design provides input overvoltage protection

to

50 V over the supply voltages. Therefore, an overvoltage

condition can exist on unselected channels without disrupting

the measured channel or operation of the MP3274! The internal

4 V reference has sufficient output current to provide other sys-

tem reference needs. Precision thin film scaling and offset resis-

tors are laser trimmed to provide for less than 2 LSB INL for +10

V inputs on all channels.

In addition, the MP3274 will output either full scale (0111 ....)

for overrange and – full scale (1000....) for underrange condi-

tions. This greatly simplifies microprocessor software develop-

ment.

SIMPLIFIED BLOCK DIAGRAM

–

+

Comp

SAR

4 V

REF

32

5

32 Ch.

MUX

AB0-4

(5 pins)

AIN0-31

(32 pins)

REF OUT

Control

Logic

GND REF.

VDAC

Latch/

Shift Register

3-State

Drivers

12

DB0-DB11

REF IN /2

12

CLK

WR RD

CS

PXS

ADEN

STL

STS

AGND

AGND

REF IN