LTC2445 datasheet(7/28 Pages) LINER

7 / 28 page

LTC2444/LTC2445/

LTC2448/LTC2449

sn2444589 2444589fs

TEST CIRCUITS

FU CTIO AL BLOCK DIAGRA

Figure 1. Functional Block Diagram

1.69k

SDO

2440 TA03

Hi-Z TO VOH

VOL TO VOH

VOH TO Hi-Z

CLOAD = 20pF

1.69k

SDO

2440 TA04

Hi-Z TO VOL

VOH TO VOL

VOL TO Hi-Z

CLOAD = 20pF

VCC

APPLICATIO S I FOR ATIO

CONVERTER OPERATION

Converter Operation Cycle

The LTC2444/LTC2445/LTC2448/LTC2449 are multi-

channel, high speed, delta-sigma analog-to-digital con-

verters with an easy to use 3- or 4-wire serial interface (see

Figure 1). Their operation is made up of three states. The

converter operating cycle begins with the conversion,

followed by the low power sleep state and ends with the

data output/input (see Figure 2). The 4-wire interface

consists of serial data input (SDI), serial data output

(SDO), serial clock (SCK) and chip select (CS). The inter-

face, timing, operation cycle and data out format is com-

patible with Linear’s entire family of ∆Σ converters.

Figure 2. LTC2444/LTC2445/LTC2448/LTC2449

State Transition Diagram

AUTOCALIBRATION

AND CONTROL

DIFFERENTIAL

3RD ORDER

∆Σ MODULATOR

DECIMATING FIR

ADDRESS

INTERNAL

OSCILLATOR

SERIAL

INTERFACE

GND

VCC

CH0

CH1

•

CH15

COM

IN+

IN–

MUX

SDO

SCK

REF+

REF –

SDI

(INT/EXT)

2444 F01

–

CONVERT

SLEEP

CHANNEL SELECT

SPEED SELECT

DATA OUTPUT

POWER UP

IN+=CH0, IN–=CH1

OSR=256,1X MODE

2444 F02

CS = LOW

AND

SCK

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