AD7793BRUZ-REEL Datasheet AD7793BRUZ-REEL, AD7793BRUZ, AD7792BRUZ-REEL | P1-P3

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

04855-001

DOUT/RD

DIN

SCLK

SERIAL

INTERFACE

AND

CONTROL

LOGIC

Σ-Δ

ADC

AD7792: 16-BIT

AD7793: 24-BIT

AIN1(+)

AIN1(–)

AIN2(+)

AIN2(–)

GND

MUX

BIAS

BAND GAP

REFERENCE

INTERNAL

CLOCK

CLK

GND

REFIN(–)/AIN3(–)

IOUT1

IOUT2

IN-AMPBUF

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

voltage of a channel to AV

/2.

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.

AD7792/AD7793

Rev. B | Page 2 of 32

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications....................................................................................... 1

Functional Block Diagram .............................................................. 1

General Description......................................................................... 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

Timing Characteristics..................................................................... 6

Timing Diagrams.......................................................................... 7

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

ESD Caution.................................................................................. 8

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

Output Noise and Resolution Specifications .............................. 11

External Reference...................................................................... 11

Internal Reference ...................................................................... 12

Typical Performance Characteristics ........................................... 13

On-Chip Registers.......................................................................... 14

Communications Register......................................................... 14

Status Register............................................................................. 15

Mode Register ............................................................................. 15

Configuration Register .............................................................. 17

Data Register............................................................................... 18

ID Register................................................................................... 18

IO Register................................................................................... 18

Offset Register ............................................................................ 19

Full-Scale Register...................................................................... 19

ADC Circuit Information.............................................................. 20

Overview ..................................................................................... 20

Digital Interface.......................................................................... 21

Circuit Description......................................................................... 24

Analog Input Channel ............................................................... 24

Instrumentation Amplifier........................................................ 24

Bipolar/Unipolar Configuration .............................................. 24

Data Output Coding .................................................................. 24

Burnout Currents ....................................................................... 25

Excitation Currents.................................................................... 25

Bias Voltage Generator .............................................................. 25

Reference ..................................................................................... 25

Reset ............................................................................................. 25

Monitor ............................................................................. 26

Calibration................................................................................... 26

Grounding and Layout .............................................................. 26

Applications Information.............................................................. 28

Temperature Measurement using a Thermocouple............... 28

Temperature Measurement using an RTD.............................. 29

Outline Dimensions ....................................................................... 30

Ordering Guide .......................................................................... 30

REVISION HISTORY

3/07—Rev. A to Rev. B

Updated Format..................................................................Universal

Change to Functional Block Diagram ........................................... 1

Changes to Specifications Section.................................................. 3

Changes to Specifications Endnote 1............................................. 5

Changes to Table 5, Table 6, and Table 7 ..................................... 11

Changes to Table 8, Table 9, and Table 10................................... 12

Changes to Table 16........................................................................ 16

Changes to Overview Section ....................................................... 20

Renamed Applications Section to Applications Information... 29

Changes to Ordering Guide .......................................................... 30

4/05—Rev. 0 to Rev. A

Changes to Absolute Maximum Ratings........................................8

Changes to Figure 17.......................................................................22

Changes to Data Output Coding Section.....................................24

Changes to Calibration Section .....................................................26

Changes to Ordering Guide...........................................................30

10/04—Revision 0: Initial Version

AD7792/AD7793

Rev. B | Page 3 of 32

SPECIFICATIONS

= 2.7 V to 5.25 V; DV

= 2.7 V to 5.25 V; GND = 0 V; all specifications T

MIN

to T

MAX

, unless otherwise noted.

Table 1.

Parameter AD7792B/AD7793B

Unit Test Conditions/Comments

ADC CHANNEL

Output Update Rate 4.17 to 470 Hz nom

No Missing Codes

24 Bits min f

ADC

< 242 Hz, AD7793

16 Bits min AD7792

Resolution See Output Noise and Resolution Specifications

Output Noise and Update Rates See Output Noise and Resolution Specifications

Integral Nonlinearity ±15 ppm of FSR max

Offset Error

±1 μV typ

Offset Error Drift vs. Temperature

±10 nV/°C typ

Full-Scale Error

3, 5

±10 μV typ

Gain Drift vs. Temperature

±1 ppm/°C typ Gain = 1 to 16, external reference

±3 ppm/°C typ Gain = 32 to 128, external reference

Power Supply Rejection 100 dB min AIN = 1 V/gain, gain ≥ 4, external reference

ANALOG INPUTS

Differential Input Voltage Ranges ±V

REF

/Gain V nom

REF

= REFIN(+) − REFIN(−) or internal reference,

gain = 1 to 128

Absolute AIN Voltage Limits

Unbuffered Mode GND – 30 mV V min Gain = 1 or 2

+ 30 mV V max

Buffered Mode GND + 100 mV V min Gain = 1 or 2

– 100 mV V max

In-Amp Active GND + 300 mV V min Gain = 4 to 128

– 1.1 V max

Common-Mode Voltage, V

0.5 V min

= (AIN(+) + AIN(−))/2, gain = 4 to 128

Analog Input Current

Buffered Mode or In-Amp Active

Average Input Current

±1 nA max Gain = 1 or 2, update rate < 100 Hz

±250 pA max Gain = 4 to 128, update rate < 100 Hz

Average Input Current Drift ±2 pA/°C typ

Unbuffered Mode Gain = 1 or 2.

Average Input Current ±400 nA/V typ Input current varies with input voltage

Average Input Current Drift ±50 pA/V/°C typ

Normal Mode Rejection

Internal Clock

@ 50 Hz, 60 Hz 65 dB min 80 dB typ, 50 ± 1 Hz, 60 ± 1 Hz, FS[3:0] = 1010

@ 50 Hz 80 dB min 90 dB typ, 50 ± 1 Hz, FS[3:0] = 1001

@ 60 Hz 90 dB min 100 dB typ, 60 ± 1 Hz, FS[3:0] = 1000

External Clock

@ 50 Hz, 60 Hz 80 dB min 90 dB typ, 50 ± 1 Hz, 60 ± 1 Hz, FS[3:0] = 1010

@ 50 Hz 94 dB min 100 dB typ, 50 ± 1 Hz, FS[3:0] = 1001

@ 60 Hz 90 dB min 100 dB typ, 60 ± 1 Hz, FS[3:0] = 1000

Common-Mode Rejection

@ DC 100 dB min AIN = 1 V/gain, gain ≥ 4

@ 50 Hz, 60 Hz

100 dB min 50 ± 1 Hz, 60 ± 1 Hz, FS[3:0] = 1010

@ 50 Hz, 60 Hz

100 dB min

50 ± 1 Hz (FS[3:0] = 1001)

, 60 ± 1 Hz

(FS[3:0] = 1000)

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27 P28-P30 P31-P32

AD7793BRUZ-REEL

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Analog Devices Inc.

Description:

Analog to Digital Converters - ADC 3Ch Lo Noise Lo Pwr 24B w/ On-Chip Ref

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AD7793BRUZ-REEL

AD7793BRUZ-REEL

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