LTC1196 datasheet(15/28 Pages) LINER

15 / 28 page

LTC1196/LTC1198

APPLICATI

I FOR ATIO

Connection to a microprocessor or a DSP serial port is

quite simple (see Data Transfer section). It requires no

additional hardware, but the speed will be limited by the

clock rate of the microprocessor or the DSP which limits

the conversion time of the LTC1196/LTC1198.

Data Transfer

Data transfer differs slightly between the LTC1196 and the

LTC1198. The LTC1196 interfaces over 3 lines: CS, CLK

and DOUT. A falling CS initiates data transfer as shown in

the LTC1196 Operating Sequence. After CS falls, the first

CLK pulse enables DOUT. After two null bits, the A/D

conversion result is output on the DOUT line. Bringing CS

high resets the LTC1196 for the next data exchange.

The LTC1198 can transfer data with 3 or 4 wires. The

additional input, DIN, is used to select the 2-channel MUX

configuration.

The data transfer between the LTC1198 and the digital

systems can be broken into two sections: Input Data Word

and A/D Conversion Result. First, each bit of the input data

word is captured on the rising CLK edge by the LTC1198.

Second, each bit of the A/D conversion result on the DOUT

line is updated on the rising CLK edge by the LTC1198.

This bit should be captured on the next rising CLK edge by

the digital systems (see A/D Conversion Result section).

Data transfer is initiated by a falling chip select (CS) signal

as shown in the LTC1198 Operating Sequence. After CS

falls the LTC1198 looks for a start bit. After the start bit is

received, the 4-bit input word is shifted into the DIN input.

The first two bits of the input word configure the LTC1198.

The last two bits of the input word allow the ADC to acquire

the input voltage by 2.5 clocks before the conversion

starts. After the conversion starts, two null bits and the

conversion result are output on the DOUT line. At the end

of the data exchange CS should be brought high. This

resets the LTC1198 in preparation for the next data ex-

change.

Input Data Word

The LTC1196 requires no DIN word. It is permanently

configured to have a single differential input. The conver-

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

sequence, followed by zeros indefinitely if clocks are

continuously applied with CS low.

The LTC1198 clocks data into the DIN input on the rising

edge of the clock. The input data word is defined as follows:

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 LTC1198 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 DINpinarethenignoreduntilthenextCScycle.

Multiplexer (MUX) Address

The 2 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 following table. In

single-ended mode, all input channels are measured with

respect to GND.

DIN1

DIN2

DOUT1

DOUT2

SHIFT MUX

ADDRESS IN

2 NULL BITS

SHIFT A/D CONVERSION

RESULT OUT

1196/98 AI01

SGL/

DIFF

ODD/

SIGN

DUMMY

START

MUX

ADDRESS

DUMMY

BITS

119698 AI02

DUMMY

LTC1198 Channel Selection

MUX ADDRESS

SGL/DIFF

ODD/SIGN

CHANNEL #

–

GND

–

SINGLE-ENDED

MUX MODE

DIFFERENTIAL

MUX MODE

1196/98 AI03

LTC1196 Datasheet(PDF) 15 Page - Linear Technology

LTC1196 Datasheet(HTML) 15 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL