LTC2302 datasheet(13/20 Pages) LINER

13 / 20 page

LTC2302/LTC2306

23026fa

APPLICATIONS INFORMATION

Figure 1a. Example MUX Conﬁgurations

Figure 1b. Changing the MUX Assignment “On the Fly”

and Control section). The input data word for the LTC2306

is deﬁned as follows:

S/D O/S

UNI

S/D = SINGLE-ENDED/DIFFERENTIAL BIT

O/S = ODD/SIGN BIT

UNI = UNIPOLAR/BIPOLAR BIT

X = DON’T CARE

For the LTC2302, the input data word is deﬁned as:

O/S

UNI

Analog Input Multiplexer

The analog input MUX is programmed by the S/D and O/S

bits of the DIN word for the LTC2306 and the O/S bit of the

DIN word for the LTC2302. Table 1 and Table 2 list MUX

conﬁgurations for all combinations of the conﬁguration

bits. Figure 1a shows several possible MUX conﬁgurations

and Figure 1b shows how the MUX can be reconﬁgured

from one conversion to the next.

Driving the Analog Inputs

The analog inputs of the LTC2302/LTC2306 are easy to

drive. Each of the analog inputs of the LTC2306 (CH0

and CH1) can be used as a single-ended input relative

to GND or as a differential pair. The analog inputs of the

LTC2302 (IN+, IN–) are always conﬁgured as a differential

pair. Regardless of the MUX conﬁguration, the “+” and “–”

inputs are sampled at the same instant. Any unwanted

signal that is common to both inputs will be reduced by

the common mode rejection of the sample-and-hold cir-

cuit. The inputs draw only one small current spike while

CH0

CH1

(–) GND

2 Single-Ended

1 Differential

+ (–)

LTC2306

23026 F01a

– (+){

CH0

CH1

1 Differential

+ (–)

LTC2302

– (+){

IN+

IN–

CH0

CH1

(–) GND

LTC2306

2nd Conversion

1st Conversion

23026 F01b

–{

CH0

CH1

LTC2306

S/D

O/S

CH0

–

CH1

–

WITH RESPECT

TO GND

NOTE: UNIPOLAR MODE SHOULD BE USED

FOR SINGLE-ENDED OPERATION, SINCE INPUT

SIGNALS ARE ALWAYS REFERENCED TO GND

Table 1. Channel Conﬁguration

for the LTC2306

O/S

IN+

–

IN–

–

Table 2. Channel Conﬁguration

for the LTC2302

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