3-Channel, Low Noise, Low Power, 16-/24-Bit - ADC with On-Chip In-Amp and Reference AD7792/AD7793 FEATURES FUNCTIONAL BLOCK DIAGRAM GND AV REFIN(+)/AIN3(+) REFIN()/AIN3() DD Up to 23 bits effective resolution RMS noise 40 nV 4.17 Hz V BIAS BAND GAP REFERENCE 85 nV 16.7 Hz GND AV DD Current: 400 A typical AIN1(+) DOUT/RDY AIN1() SERIAL MUX Power-down: 1 A maximum DIN INTERFACE AIN2(+) - BUF IN-AMP AND ADC AIN2() SCLK Low noise programmable gain instrumentation amp CONTROL LOGIC CS Band gap reference with 4 ppm/C drift typical AV DD GND DV DD Update rate: 4.17 Hz to 470 Hz IOUT1 INTERNAL AD7792: 16-BIT CLOCK AD7793: 24-BIT 3 differential inputs IOUT2 Internal clock oscillator CLK Simultaneous 50 Hz/60 Hz rejection Figure 1. Programmable current sources GENERAL DESCRIPTION On-chip bias voltage generator The AD7792/AD7793 are low power, low noise, complete Burnout currents analog front ends for high precision measurement applications. Power supply: 2.7 V to 5.25 V The AD7792/AD7793 contain a low noise 16-/24-bit - ADC 40C to +105C temperature range with three differential analog inputs. The on-chip, low noise Independent interface power supply instrumentation amplifier means that signals of small ampli- 16-lead TSSOP package tude can be interfaced directly to the ADC. With a gain Interface setting of 64, the rms noise is 40 nV when the update rate 3-wire serial equals 4.17 Hz. SPI, QSPI, MICROWIRE, and DSP compatible Schmitt trigger on SCLK The devices contain a precision low noise, low drift internal band gap reference and can accept an external differential APPLICATIONS reference. Other on-chip features include programmable Thermocouple measurements excitation current sources, burnout currents, and a bias voltage RTD measurements generator. The bias voltage generator sets the common-mode Thermistor measurements voltage of a channel to AVDD/2. Gas analysis The devices can be operated with either the internal clock or an Industrial process control external clock. The output data rate from the parts is software- Instrumentation programmable and can be varied from 4.17 Hz to 470 Hz. Portable instrumentation Blood analysis The parts operate with a power supply from 2.7 V to 5.25 V. Smart transmitters They consume a current of 400 A typical and are housed in a Liquid/gas chromatography 16-lead TSSOP package. 6-digit DVM Rev. B 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 20042007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 04855-001AD7792/AD7793 TABLE OF CONTENTS Features .............................................................................................. 1 Offset Register ............................................................................ 19 Applications....................................................................................... 1 Full-Scale Register...................................................................... 19 Functional Block Diagram .............................................................. 1 ADC Circuit Information.............................................................. 20 General Description ......................................................................... 1 Overview ..................................................................................... 20 Revision History ............................................................................... 2 Digital Interface.......................................................................... 21 Specifications..................................................................................... 3 Circuit Description......................................................................... 24 Timing Characteristics..................................................................... 6 Analog Input Channel ............................................................... 24 Timing Diagrams.......................................................................... 7 Instrumentation Amplifier........................................................ 24 Absolute Maximum Ratings............................................................ 8 Bipolar/Unipolar Configuration .............................................. 24 ESD Caution.................................................................................. 8 Data Output Coding .................................................................. 24 Pin Configuration and Function Descriptions............................. 9 Burnout Currents ....................................................................... 25 Output Noise and Resolution Specifications .............................. 11 Excitation Currents .................................................................... 25 External Reference...................................................................... 11 Bias Voltage Generator .............................................................. 25 Internal Reference ...................................................................... 12 Reference ..................................................................................... 25 Typical Performance Characteristics ........................................... 13 Reset ............................................................................................. 25 On-Chip Registers.......................................................................... 14 AV Monitor ............................................................................. 26 DD Communications Register......................................................... 14 Calibration................................................................................... 26 Status Register............................................................................. 15 Grounding and Layout .............................................................. 26 Mode Register ............................................................................. 15 Applications Information .............................................................. 28 Configuration Register .............................................................. 17 Temperature Measurement using a Thermocouple............... 28 Data Register ............................................................................... 18 Temperature Measurement using an RTD.............................. 29 ID Register................................................................................... 18 Outline Dimensions....................................................................... 30 IO Register................................................................................... 18 Ordering Guide .......................................................................... 30 REVISION HISTORY 3/07Rev. A to Rev. B Updated Format..................................................................Universal 4/05Rev. 0 to Rev. A Change to Functional Block Diagram ........................................... 1 Changes to Absolute Maximum Ratings........................................8 Changes to Specifications Section.................................................. 3 Changes to Figure 17.......................................................................22 Changes to Specifications Endnote 1............................................. 5 Changes to Data Output Coding Section.....................................24 Changes to Table 5, Table 6, and Table 7 ..................................... 11 Changes to Calibration Section .....................................................26 Changes to Table 8, Table 9, and Table 10 ................................... 12 Changes to Ordering Guide ...........................................................30 Changes to Table 16........................................................................ 16 10/04Revision 0: Initial Version Changes to Overview Section ....................................................... 20 Renamed Applications Section to Applications Information... 29 Changes to Ordering Guide .......................................................... 30 Rev. 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