AD7793B datasheet, PDF - EEWORLD Datasheet

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AD7793B: DescriptionLow Power, 16/24-Bit Sigma-Delta ADC with Low-Noise In-Amp and Embedded Reference; File Size237KB，18 Pages; ManufacturerADI; Websitehttps://www.analog.com

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AD7793B Overview

Low Power, 16/24-Bit Sigma-Delta ADC with Low-Noise In-Amp and Embedded Reference

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Preliminary Technical Data

FEATURES

Resolution:

Low Power, 16/24-Bit Sigma-Delta ADC with

Low-Noise In-Amp and Embedded Reference

AD7792/AD7793

GND

VBIAS

VDD

BANDGAP

REFERENCE

AVDD

REFIN(+)/AIN3(+)

REFIN(-)/AIN3(-)

GND

SIGMA DELTA

ADC

SERIAL

INTERFACE

AND

CONTROL

LOGIC

DOUT/RDY

DIN

SCLK

AIN1(+)

AIN1(-)

AIN2(+)

AIN2(-)

VDD

IOUT1

IOUT2

GND

INTERNAL

CLOCK

MUX

IN-AMP

AD7792: 16-Bit

AD7793: 24-Bit

Low Noise Programmable Gain Instrumentation-Amp

RMS noise: 80 nV (Gain = 64)

Bandgap Reference with 5ppm/ C Drift typ

Power

Supply: 2.7 V to 5.25 V operation

Normal: 400 µA typ

Power-down: 1 µA max

Update Rate: 4 Hz to 500 Hz

Simultaneous 50 Hz/60 Hz Rejection

Internal Clock Oscillator

Programmable Current Sources (10 µA/200 µA/1 mA)

On-Chip Bias Voltage Generator

100 nA Burnout Currents

Independent Interface Power Supply

16-Lead TSSOP Package

DVDD

AD7792/AD7793

CLK

Figure 1.

GENERAL DESCRIPTION

The AD7792/AD7793 is a low power, complete analog front end

for low frequency measurement applications. The

AD7792/AD7793 contains a low noise 16/24-bit ∑-∆ ADC with

three differential analog inputs. The on-chip low noise

instrumentation amplifier means that signals of small

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

setting of 64, the rms noise is 80 nV when the update rate equals

16.6 Hz.

The device contains a precision low noise, low drift internal

bandgap reference for absolute measurements. An external

reference can also be used if ratiometric measurements are re-

quired. On-chip programmable excitation current sources can

be used to supply a constant current to RTDs and thermistors

while the 100 nA burnout currents can be used to ensure that

the sensors connected to the ADC are not burnt out. For ther-

mocouple applications, the on-chip bias voltage generator steps

up the common mode voltage from the thermocouple so that it

is within the ADC’s allowable range.

The device can be operated with the internal clock or, alterna-

tively, an external clock can be used if synchronizing several

devices. The output data rate from the part is software pro-

grammable and can be varied from 4 Hz to 500 Hz.

The part operates with a power supply from 2.7 V to 5.25 V. It

consumes a current of 450 uA maximum and is housed in a 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

FUNCTIONAL BLOCK DIAGRAM

REV.PrF

6/04.

Information furnished by Analog Devices is believed to be accurate and reliable.

However, no responsibility is assumed by Analog Devices for its use, nor for any

infringements of patents or other rights of third parties that may result from its use.

Specifications subject to change without notice. No license is granted by implication

or otherwise under any patent or patent rights of Analog Devices. Trademarks and

registered trademarks are the property of their respective companies.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

www.analog.com

Tel: 781.329.4700

Fax: 781.326.8703

AD7792/AD7793

TABLE OF CONTENTS

AD7792/AD7793—Specifications.................................................. 3

Timing Characteristics

.................................................................... 6

Absolute Maximum Ratings............................................................ 8

Pin Configuration and Function Descriptions............................. 9

Typical Performance Characteristics ........................................... 11

On-chip Registers ........................................................................... 12

Communications Register (RS2, RS1, RS0 = 0, 0, 0) .............. 12

Status Register (RS2, RS1, RS0 = 0, 0, 0; Power-on/Reset =

0x80 (AD7792) / 0x88 (AD7793)) ........................................... 13

Mode Register (RS2, RS1, RS0 = 0, 0, 1; Power-on/Reset =

0x000A)........................................................................................ 13

Configuration Register (rs2, RS1, RS0 = 0, 1, 0; Power-

on/Reset = 0x0710) .................................................................... 15

Data Register (RS2, RS1, RS0 = 0, 1, 1; Power-on/Reset =

0x0000(00)) ................................................................................. 16

ID Register (RS2, RS1, RS0 = 1, 0, 0; Power-on/Reset = 0xXA

(ad7792) / 0xXB (ad7793))........................................................ 16

IO Register (RS2, RS1, RS0 = 1, 0, 1; Power-on/Reset = 0x00)

....................................................................................................... 16

OFFSET Register (RS2, RS1, RS0 = 1, 1, 0; Power-on/Reset =

0x8000(AD7792)/ 0x800000(AD7793)).................................. 17

FULL-SCALE Register (RS2, RS1, RS0 = 1, 1, 1; Power-

Preliminary Technical Data

on/Reset = 0x5xx5(AD7792)/ 0x5xXXx5(AD7793)) ............ 17

ADC Circuit Information.............................................................. 19

Overview ..................................................................................... 19

Noise Performance ..................................................................... 19

Digital Interface .......................................................................... 20

Single Conversion Mode ....................................................... 21

Continuous Conversion Mode............................................. 21

Continuous Read Mode ........................................................ 22

Circuit Description......................................................................... 23

Analog Input Channel ............................................................... 23

Bipolar/Unipolar Configuration .............................................. 23

Data Output Coding .................................................................. 23

Reference ..................................................................................... 23

Monitor ................................................................................ 24

Grounding and Layout .............................................................. 24

Outline Dimensions ....................................................................... 26

ESD Caution................................................................................ 26

REVISION HISTORY

REV.PrF, June 2004: Initial Version

REV.PrF 6/04 | Page 2

AD7793B Related Products

	AD7793B	AD7792	AD7793
Description	Low Power, 16/24-Bit Sigma-Delta ADC with Low-Noise In-Amp and Embedded Reference	Low Power, 16/24-Bit Sigma-Delta ADC with Low-Noise In-Amp and Embedded Reference	Low Power, 16/24-Bit Sigma-Delta ADC with Low-Noise In-Amp and Embedded Reference

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