LTC1098AC datasheet(15/28 Pages) LINER

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LTC1096/LTC1096L

LTC1098/LTC1098L

SGL/

DIFF

ODD/

SIGN

MSBF

START

MUX

ADDRESS

MSB-FIRST/

LSB-FIRST

LTC1096/8 • AI02

Start Bit

The first “logical one” clocked into the DIN input after CS

goes low is the start bit. The start bit initiates the data

transfer. The LTC1098(L) will ignore all leading zeros

which precede this logical one. After the start bit is

received, the remaining bits of the input word will be

clocked in. Further inputs on the DIN pin are then ignored

until the next CS cycle.

Multiplexer (MUX) Address

The bits of the input word following the START bit assign

the MUX configuration for the requested conversion. For

a given channel selection, the converter will measure the

voltage between the two channels indicated by the “+” and

“–” signs in the selected row of the followintg tables. In

single-ended mode, all input channels are measured with

respect to GND.

MSB-First/LSB-First (MSBF)

The output data of the LTC1098(L) is programmed for

MSB-first or LSB-first sequence using the MSBF bit.

When the MSBF bit is a logical one, data will appear on

the DOUT line in MSB-first format. Logical zeros will be

filled in indefinitely following the last data bit. When the

MSBF bit is a logical zero, LSB-first data will follow the

normal MSB-first data on the DOUT line. (see Operating

Sequence)

Unipolar Transfer Curve

The LTC1096(L)/LTC1098(L) are permanently config-

ured for unipolar only. The input span and code assign-

ment for this conversion type are shown in the follow-

ing figures for a 5V reference.

Unipolar Transfer Curve

VIN

0 0 0 0 0 0 0 1

0 0 0 0 0 0 0 0

1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 0

•

LTC1096/8 • AI04

the A/D conversion result is output on the DOUT line.

Bringing CS high resets the LTC1096(L) for the next data

exchange.

Input Data Word

The LTC1096(L) requires no DIN word. It is permanently

configured to have a single differential input. The conver-

sion result, in which output on the DOUT line is MSB-first

sequence, followed by LSB sequence providing easy inter-

face to MSB- or LSB-first serial ports.

The LTC1098(L) clocks data into the DIN input on the rising

edge of the clock. The input data words are defined as

follows:

APPLICATI

I FOR ATIO

LTC1098(L) Channel Selection

MUX ADDRESS

SGL/DIFF

ODD/SIGN

CHANNEL #

–

GND

–

SINGLE-ENDED MUX MODE

DIFFERENTIAL MUX MODE

LTC1096/8 • AI03

Operation with DIN and DOUT Tied Together

The LTC1098(L) can be operated with DIN and DOUT tied

together. This eliminates one of the lines required to

communicate to the microprocessor (MPU). Data is trans-

mitted in both directions on a single wire. The processor

pin connected to this data line should be configurable as

either an input or an output. The LTC1098(L) will take

control of the data line and drive it low on the 4th falling

Unipolar Output Code

OUTPUT CODE

1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 0

•

0 0 0 0 0 0 0 1

0 0 0 0 0 0 0 0

INPUT VOLTAGE

VREF – 1LSB

VREF – 2LSB

•

1LSB

INPUT VOLTAGE

(VREF = 5.000V)

4.9805V

4.9609V

•

0.0195V

LTC1096/8 • AI05

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