LTC1198 View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC1198

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

Linear Technology 

APPLICATIONS INFORMATION

CS

1

2

3

CLK

LTC1196/LTC1198

DUMMY BITS LATCHED

BY LTC1198

4

5

DATA (DIN/DOUT)

START

SGL/DIFF

ODD/SIGN

DUMMY

THE DIGITAL SYSTEM CONTROLS DATA LINE

AND SENDS MUX ADDRESS TO LTC1198

THE DIGITAL SYSTEM MUST RELEASE

DATA LINE AFTER 5TH RISING CLK

AND BEFORE THE 5TH FALLING CLK

LTC1198 CONTROLS DATA LINE AND SENDS

A/D RESULT BACK TO THE DIGITAL SYSTEM

LTC1198 TAKES CONTROL OF

DATA LINE ON 5TH FALLING CLK

1196/98 F04

Figure 4. LTC1198 Operation with DIN and DOUT Tied Together

10

LT1198 VCC = 5V

1

LT1196 VCC = 2.87V

0.1

LT1198 VCC = 5V

0.01

LT1198 VCC = 2.87V

Minimize CS Low Time (LTC1198)

In systems that have significant time between conver-

sions, lowest power drain will occur with the minimum

CS low time. Bringing CS low, transfering data as quickly

as possible, then bringing it back high will result in the

lowest current drain. This minimizes the amount of time

the device draws power.

0.001

100

1k

10k

100k

1M

SAMPLE RATE (Hz)

1196/98 F05

Figure 5. Supply Current vs Sample Rate for LTC1196/LTC1198

Operating on 5V and 2.7V Supplies

When the CS pin is high (= supply voltage), the LTC1198

is in shutdown mode and draws only leakage current.

The status of the DIN and CLK input has no effect on the

supply current during this time. There is no need to stop

DIN and CLK with CS = high; they can continue to run

without drawing current.

OPERATING ON OTHER THAN 5V SUPPLIES

The LTC1196/LTC1198 operate from single 2.7V to 6V

supplies. To operate the LTC1196/LTC1198 on other than

5V supplies, a few things must be kept in mind.

Input Logic Levels

The input logic levels of CS, CLK and DIN are made to meet

TTL on 5V supply. When the supply voltage varies, the input

logic levels also change (see typical curve of Digital Input

Logic Threshold vs Supply Voltage). For these two ADCs

to sample and convert correctly, the digital inputs have

to be in the logical low and high relative to the operating

supply voltage. If achieving micropower consumption is

desirable on the LTC1198, the digital inputs must go rail-

to-rail between supply voltage and ground (see Reducing

Power Consumption section).

119698fa

17

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