Datasheet AD7796, AD7797 (Analog Devices)

Low Power, 16-/24-Bit Sigma-Delta ADC for Bridge Sensors Low Power, 16-/24-Bit Data Sheet AD7796/ AD7797 FEATURES FUNCTIONAL BLOCK DIAGRAM RMS noise: 65 nV GND AVDD REFIN(+) REFIN(–) Instrumentation amp AD7796: 16-BIT ADC AVDD AD7797: 24-BIT ADC Temperature sensor Internal clock oscillator AIN(+) SERIAL DOUT/RDY INTERFACE AIN(–) DIN Σ-Δ Simultaneous 50 Hz/60 Hz rejection MUX ×128 AND ADC SCLK CONTROL LOGIC Update rate range: 4.17 Hz to 123 Hz CS Current: 250 µA typ GND REFERENCE INTERNAL DV Power-down: 1 µA DD TEMP AD7796/ CLOCK SENSOR Power supply range: 2.7 V to 5.25 V AD7797
001
–40°C to +85°C temperature range CLK
06083-
Independent interface power supply
Figure 1.
16-lead TSSOP INTERFACE 3-wire serial SPI, QSPI™, MICROWIRE, and DSP compatible Schmitt trigger on SCLK APPLICATIONS Weigh scales Strain gages Industrial process control Instrumentation Portable instrumentation GENERAL DESCRIPTION
The AD7796/AD7797 are complete, analog front ends for high The devices can be operated with the internal clock or an external precision, bridge sensor applications such as weigh scales. The clock. The output data rate from the devices is software- AD7796/AD7797 contain a Σ-∆ ADC capable of 16-/24-bit programmable and can be varied from 4.17 Hz to 123 Hz. resolution, respectively. The on-chip instrumentation amplifier has a fixed gain of 128, allowing small amplitude signals such as The AD7796/AD7797 operate with a power supply from 2.7 V those from bridge sensors to be directly interfaced to the ADC. to 5.25 V. Each device consumes a current of 250 µA typical and is housed in a 16-lead TSSOP. Each device has one differential input and contains a temperature sensor that is internal y connected to the ADC. This sensor can be used to perform temperature compensation of the bridge.
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Document Outline FEATURES INTERFACE APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING CHARACTERISTICS TIMING DIAGRAMS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS RMS NOISE AND RESOLUTION SPECIFICATIONS TYPICAL PERFORMANCE CHARACTERISTICS ON-CHIP REGISTERS COMMUNICATION REGISTER RS2, RS1, RS0 = 0, 0, 0 STATUS REGISTER RS2, RS1, RS0 = 0, 0, 0; Power-On/Reset = 0x80 MODE REGISTER RS2, RS1, RS0 = 0, 0, 1; Power-On/Reset = 0x000A CONFIGURATION REGISTER RS2, RS1, RS0 = 0, 1, 0; Power-On/Reset = 0x0710 DATA REGISTER RS2, RS1, RS0 = 0, 1, 1; Power-On/Reset = 0x0000 (AD7796)/0x000000 (AD7797) ID REGISTER RS2, RS1, RS0 = 1, 0, 0; Power-On/Reset = 0x5A (AD7796)/0x5B (AD7797) OFFSET REGISTER RS2, RS1, RS0 = 1, 1, 0; Power-On/Reset = 0x8000 (AD7796)/0x800000 (AD7797) FULL-SCALE REGISTER RS2, RS1, RS0 = 1, 1, 1; Power-On/Reset = 0x5XXX (AD7796)/0x5XXX00 (AD7797) ADC CIRCUIT INFORMATION OVERVIEW DIGITAL INTERFACE Single Conversion Mode Continuous Conversion Mode Continuous Read Mode CIRCUIT DESCRIPTION ANALOG INPUT CHANNEL BIPOLAR/UNIPOLAR CONFIGURATION DATA OUTPUT CODING REFERENCE RESET BURNOUT CURRENTS AVDD MONITOR TEMPERATURE MONITOR CALIBRATION GROUNDING AND LAYOUT APPLICATIONS INFORMATION WEIGH SCALES OUTLINE DIMENSIONS ORDERING GUIDE