3-Channel, Low Noise, Low Power, 16-/24-Bit

∑-Δ ADC with On-Chip In-Amp and Reference

AD7792/AD7793

Rev. B

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FEATURES

Up to 23 bits effective resolution

RMS noise

40 nV @ 4.17 Hz

85 nV @ 16.7 Hz

Current: 400 μA typical

Power-down: 1 μA maximum

Low noise programmable gain instrumentation amp

Band gap reference with 4 ppm/°C drift typical

Update rate: 4.17 Hz to 470 Hz

3 differential inputs

Internal clock oscillator

Simultaneous 50 Hz/60 Hz rejection

Programmable current sources

On-chip bias voltage generator

Burnout currents

Power supply: 2.7 V to 5.25 V

–40°C to +105°C temperature range

Independent interface power supply

16-lead TSSOP package

Interface

3-wire serial

SPI®, QSPI™, MICROWIRE™, and DSP compatible

Schmitt trigger on SCLK

APPLICATIONS

Thermocouple measurements

RTD measurements

Thermistor measurements

Gas analysis

Industrial process control

Instrumentation

Portable instrumentation

Blood analysis

Smart transmitters

Liquid/gas chromatography

6-digit DVM

FUNCTIONAL BLOCK DIAGRAM

DOUT/RDY

DIN

SCLK

CS

SERIAL

INTERFACE

AND

CONTROL

LOGIC

Σ-Δ

ADC

AD7792: 16-BIT

AD7793: 24-BIT

AIN1(+)

AIN1(–)

AIN2(+)

AIN2(–)

GND

MUX

BAND GAP

REFERENCE

INTERNAL

CLOCK

CLK

GND

GND

REFIN(–)/AIN3(–)

IOUT1

IOUT2

IN-AMP

BUF

REFIN(+)/AIN3(+)

Figure 1.

GENERAL DESCRIPTION

The AD7792/AD7793 are low power, low noise, complete

analog front ends for high precision measurement applications.

The AD7792/AD7793 contain a low noise 16-/24-bit ∑-Δ ADC

with three differential analog inputs. The on-chip, low noise

instrumentation amplifier means that signals of small ampli-

tude can be interfaced directly to the ADC. With a gain

setting of 64, the rms noise is 40 nV when the update rate

equals 4.17 Hz.

The devices contain a precision low noise, low drift internal

band gap reference and can accept an external differential

reference. Other on-chip features include programmable

excitation current sources, burnout currents, and a bias voltage

generator. The bias voltage generator sets the common-mode

The devices can be operated with either the internal clock or an

external clock. The output data rate from the parts is software-

programmable and can be varied from 4.17 Hz to 470 Hz.

The parts operate with a power supply from 2.7 V to 5.25 V.

They consume a current of 400 μA typical and are housed in a

16-lead TSSOP package.