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AD7783

Read-Only, Pin Configured 24-Bit - ADC

with Excitation Current Sources

FEATURES

Single-Channel, 24-Bit

-

ADC

Pin Configurable (No Programmable Registers)

ISOURCE Select™

Pin Programmable Input Ranges (

±2.56 V or ±160 mV)

Fixed 19.79 Hz Update Rate

Simultaneous 50 Hz and 60 Hz Rejection

24-Bit No Missing Codes

18.5-Bit p-p Resolution (

±2.56 V Range)

16.5-Bit p-p Resolution (

±160 mV Range)

INTERFACE

Master or Slave Mode of Operation

Slave Mode

3-Wire Serial

Schmitt Trigger on SCLK

POWER

Specified for Single 3 V and 5 V Operation

Normal: 1.3 mA @ 3 V

Power-Down: 9

A

ON-CHIP FUNCTIONS

Rail-to-Rail Input Buffer and PGA

APPLICATIONS

Sensor Measurement

Industrial Process Control

Temperature Measurement

Pressure Measurement

Weigh Scales

Portable Instrumentation

GENERAL DESCRIPTION

The AD7783 is a complete analog front end for low frequency

measurement applications. The 24-bit sigma-delta ADC con-

tains one fully differential input channel that can be configured

with a gain of 1 or 16 allowing full-scale input signal ranges of

±2.56 V or ±160 mV from a +2.5 V differential reference input.

It also contains two 200

mA integrated current sources.

The AD7783 has an extremely simple, read-only digital inter-

face that can be operated in master mode or slave mode.

There are no on-chip registers to be programmed. The input

signal range and current source selection are configured using

two external pins.

FUNCTIONAL BLOCK DIAGRAM

OSCILLATOR

AND

PLL

DOUT/

RDY

SCLK

MODE

XTAL1 XTAL2

SERIAL

INTERFACE

AND

CONTROL

LOGIC

CS

REFIN(–)

REFIN(+)

24-BIT

-

ADC

RANGE

AD7783

GND

BUF

PGA

MUX

AIN(+)

AIN(–)

IOUT1

IEXC1

200 A

IEXC2

200 A

IOUT2

IPIN

BASIC CONNECTION DIAGRAM

AD7783

REFIN(+)

REFIN(–)

AIN(–)

AIN(+)

IOUT2

IOUT1

XTAL1

DOUT/

RDY

CS

SCLK

XTAL2

GND

REFERENCE

INPUT

CURRENT

SOURCES

ANALOG

INPUT

POWER SUPPLY

32.768kHz

CRYSTAL

DIGITAL

INTERFACE

The device operates from a 32.768 kHz crystal with an on-chip

PLL generating the required internal operating frequency. The

output data rate from the part is fixed via the master clock at

19.79 Hz and provides simultaneous 50 Hz and 60 Hz rejection

at this update rate. At this update rate, 18-bit p-p resolution can

be obtained.

The part operates from a single 3 V or 5 V supply. When oper-

ating from 3 V supplies, the power dissipation for the part is

3.9 mW. The AD7783 is available in a 16-lead TSSOP.

Another part in the AD778x family is the AD7782. It is similar

to the AD7783 except it has no integrated current sources and

two differential input channels.