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© 1996 Wolfson Microelectronics

WM0834, WM0838

Production Data

Sept 1996 Rev 2.0

8-Bit ADCs with Serial Interface and

Configurable Input Multiplexer

Description

WM0834 and WM0838 are 8-bit analogue to digital

converters (ADC) with configurable 4-input and 8-input

multiplexers respectively and a serial I/O interface.

Assignment of the multiplexer inputs is configured before

each conversion via the serial data input to give single-ended

or differential operation for the selected inputs. A mixture of

input configurations can be used in the same application.

WM0838 also has a pseudo-differential configuration where

all 8 inputs can be refered to a common input at an arbitrary

voltage.

Serial communcation with WM0834/8 is via Data In (DI) and

Data Out (DO) wires under the control of clock and chip

select inputs. A high output at the SARS pin indicates when

the conversion is in progress. To initiate a conversion chip

enable is held low and data is input to DI on the rising edge

of the clock, comprising, a start bit, and bits to set up the

input configuration and polarity. After a half clock cycle delay

conversion results appear at DO on the falling edge of the

clock, MSB first, concurrently with A-D conversion. This is

followed by the results LSB first, indicated by the falling edge

of SARS. WM0838 has a shift enable (SE) input used to

control the LSB first output on DO.

WM0834/8 operate on 5V and 3.3V supply voltages and

are available in small outline and DIP packages for com-

ture ranges.

Features

•

Functionally Equivalent to National Semiconduc-

tor ADC0834 and ADC0838 without the Internal

Zener Regulator Network

•

4-input (WM0834) or 8-input (WM0838) MUX

options

•

Reference input operates ratiometrically or with

a fixed reference

•

Input range 0 to Vcc with Vcc Reference

•

5V and 3.3V variants

•

Total Unadjusted Error: ± 1 LSB

•

8-bit resolution

•

Low Power

•

32

µµµµµs conversion time at fclock = 250 kHz

•

Serial I/O interface

•

WM0834 packages: 14 pin SO & DIP

WM0838 packages: 20 pin wide-body SO & DIP

Applications

•

Embedding with remote sensors

•

Equipment health monitoring

•

Automotive

•

Industrial control

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

COM

1

AGND

DI

CLK

CS

Notes:

1. Internally tied to AGND for WM0834

2. Not available on WM0834

WM0834

4 Inputs

WM0838

8 Inputs

DO

SARS

DGND

SE

2

Vcc

Input

MUX

Output Shift

Register

Comparator

Start Conv

Mux Select

WM0834/8

DAC

&

SAR

Logic

Input Latch

Internal CS