LTC1196 查看數據表（PDF） - Linear Technology

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LTC1196

8-Bit, SO-8, 1Msps ADCs with Auto-Shutdown Options

Linear Technology 

LTC1196/LTC1198

APPLICATIONS INFORMATION

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 ad-

ditional 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

exchange.

Input Data Word

The LTC1196 requires no DIN word. It is permanently con-

figured to have a single differential input. The conversion

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 ris-

ing edge of the clock. The input data word is defined

as follows:

START

SGL/

DIFF

ODD/

SIGN

DUMMY DUMMY

Start Bit

MUX

ADDRESS

DUMMY

BITS

119698 AI02

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 DIN pin are then ignored until the

next CS cycle.

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.

CS

SHIFT MUX

ADDRESS IN

DIN1

DOUT1

DIN2

2 NULL BITS SHIFT A/D CONVERSION

RESULT OUT

DOUT2

1196/98 AI01

LTC1198 Channel Selection

SINGLE-ENDED

MUX MODE

DIFFERENTIAL

MUX MODE

MUX ADDRESS

SGL/DIFF ODD/SIGN

1

0

1

1

0

0

0

1

CHANNEL #

0

1 GND

+

–

+–

+

–

–

+

1196/98 AI03

119698fa

15

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