3-Channel, Low Noise, Low Power, 16-/24-Bit, - ADC with On-Chip In-Amp Data Sheet AD7798/AD7799 FEATURES FUNCTIONAL BLOCK DIAGRAM GND AV REFIN(+) REFIN() DD RMS noise: 27 nV at 4.17 Hz (AD7799) REFERENCE DETECT AD7798/AD7799 65 nV at 16.7 Hz (AD7799) 40 nV at 4.17 Hz (AD7798) AIN1(+) AV DD 85 nV at 16.7 Hz (AD7798) AIN1() Current: 380 A typical DOUT/RDY AIN2(+) SERIAL MUX AIN2() INTERFACE DIN Power-down: 1 A maximum - IN-AMP AIN3(+)/P1 AND ADC SCLK CONTROL AIN3()/P2 Low noise, programmable gain, instrumentation amp LOGIC CS Update rate: 4.17 Hz to 470 Hz GND DV DD 3 differential inputs PSW INTERNAL AD7798: 16-BIT CLOCK AD7799: 24-BIT Internal clock oscillator GND Simultaneous 50 Hz/60 Hz rejection Figure 1. Reference detect Low-side power switch Programmable digital outputs GENERAL DESCRIPTION Burnout currents The AD7798/AD7799 are low power, low noise, complete Power supply: 2.7 V to 5.25 V analog front ends for high precision measurement applications. 40C to +105C temperature range The AD7798/AD7799 contains a low noise, 16-/24-bit - Independent interface power supply ADC with three differential analog inputs. The on-chip, low 16-lead TSSOP package noise instrumentation amplifier means that signals of small INTERFACE amplitude can be interfaced directly to the ADC. With a gain 3-wire serial setting of 64, the rms noise is 27 nV for the AD7799 and 40 nV SPI, QSPI, MICROWIRE, and DSP compatible for the AD7798 when the update rate equals 4.17 Hz. Schmitt trigger on SCLK On-chip features include a low-side power switch, reference detect, programmable digital output pins, burnout currents, APPLICATIONS and an internal clock oscillator. The output data rate from the Weigh scales part is software-programmable and can be varied from 4.17 Hz Pressure measurement to 470 Hz. Strain gauge transducers The part operates with a power supply from 2.7 V to 5.25 V. Gas analysis Industrial process control The AD7798 consumes a current of 300 A typical, whereas the Instrumentation AD7799 consumes 380 A typical. Both devices are housed in a Portable instrumentation 16-lead TSSOP package. Blood analysis Smart transmitters Liquid/gas chromotography 6-digit DVM Rev. B Document Feedback 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 20052013 Analog Devices, Inc. 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Technical Support www.analog.com 04856-001AD7798/AD7799 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 IO Register................................................................................... 17 Interface ............................................................................................. 1 Offset Register ............................................................................ 17 Applications ....................................................................................... 1 Full-Scale Register ...................................................................... 17 Functional Block Diagram .............................................................. 1 ADC Circuit Information.............................................................. 18 General Description ......................................................................... 1 Overview ..................................................................................... 18 Revision History ............................................................................... 2 Digital Interface .......................................................................... 19 Specifications ..................................................................................... 3 Circuit Description......................................................................... 22 Timing Characteristics ..................................................................... 6 Analog Input Channel ............................................................... 22 Absolute Maximum Ratings ............................................................ 8 Instrumentation Amplifier........................................................ 22 ESD Caution .................................................................................. 8 Bipolar/Unipolar Configuration .............................................. 22 Pin Configuration and Function Descriptions ............................. 9 Data Output Coding .................................................................. 23 Output Noise and Resolution Specifications .............................. 10 Burnout Currents ....................................................................... 23 AD7798 ........................................................................................ 10 Reference ..................................................................................... 23 AD7799 ........................................................................................ 11 Reference Detect ......................................................................... 23 Typical Performance Characteristics ........................................... 12 Reset ............................................................................................. 23 On-Chip Registers .......................................................................... 13 AVDD Monitor ............................................................................. 24 Communication Register .......................................................... 13 Calibration................................................................................... 24 Status Register ............................................................................. 14 Grounding and Layout .............................................................. 25 Mode Register ............................................................................. 14 Applications Information .............................................................. 26 Configuration Register .............................................................. 16 Weigh Scales ................................................................................ 26 Data Register ............................................................................... 17 Outline Dimensions ....................................................................... 27 ID Register ................................................................................... 17 Ordering Guide .......................................................................... 27 REVISION HISTORY 7/13Rev. A to Rev. B Changes to Table 3 ............................................................................ 8 Changes to Digital Interface Section ............................................ 19 Changes to Ordering Guide .......................................................... 27 3/07Rev. 0 to Rev. A Updated Format .................................................................. Universal Changes to Specifications ................................................................ 3 Changes to Table 5 and Table 6 ..................................................... 10 Changes to Table 7 and Table 8 ..................................................... 11 Changes to Table 14 ........................................................................ 15 Changes to Ordering Guide .......................................................... 27 1/05Revision 0: Initial Version Rev. B Page 2 of 28