ADC0833 datasheet(9/20 Pages) NSC

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Timing Diagram

TLH5607 – 5

Functional Description

10 MULTIPLEXER ADDRESSING

The design of the ADC0833 utilizes a sample-data compar-

ator structure which provides for a differential analog input

to be converted by a successive approximation routine

The actual voltage converted is always the difference be-

tween an assigned ‘‘a’’ input terminal and a ‘‘b’’ input ter-

minal The polarity of each input terminal of the pair being

converted indicates which line the converter expects to be

the most positive If the assigned ‘‘a’’ input is less than the

‘‘b’’ input the converter responds with an all zeros output

code

A unique input multiplexing scheme has been utilized to pro-

vide multiple analog channels with software-configurable

single-ended (ground referred) or differential inputs The an-

alog signal conditioning required in transducer-based data

acquisition systems is significantly simplified with this type

of input flexibility One converter package can now handle

ground referenced inputs and true differential inputs

A particular input configuration is assigned during the MUX

addressing sequence prior to the start of a conversion The

MUX address selects which of the analog inputs are to be

enabled and whether this input is single-ended or differen-

tial In the differential case it also assigns the polarity of the

channels Differential inputs are restricted to adjacent chan-

nel pairs For example channel 0 and channel 1 may be

selected as a differential pair Channel 0 or 1 cannot act

differentially with any other channel In addition to selecting

differential mode the sign may also be selected Channel 0

may be selected as the positive input and channel 1 as the

negative input or vice versa This programmability is best

illustrated by the MUX addressing codes shown in the fol-

lowing table The MUX address is shifted into the converter

through the DI line

TABLE I MUX Addressing

Single-Ended MUX Mode

Address

Channel

SGL

ODD

SELECT

0123

DIF

SIGN

COM is internally ties to a GND

Differential MUX Mode

Address

Channel

SGL

ODD

SELECT

0123

DIF

SIGN

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