Datasheet AD7796, AD7797 (Analog Devices) - 23

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Data Sheet AD7796/AD7797 APPLICATIONS INFORMATION
The AD7796/AD7797 offer a high resolution analog-to-digital scale output range from the transducer is 10 mV when the function. Because the analog-to-digital function is provided by sensitivity is 2 mV/V. The excitation voltage for the bridge can a Σ-∆ architecture, the devices are more immune to noisy be used to directly provide the reference for the ADC because environments, making them ideal for use in sensor measurement, the reference input range includes the supply voltage. This al ows a and industrial and process-control applications. ratiometric measurement. Therefore, variations of the excitation voltage do not affect the measurement.
WEIGH SCALES
The on-chip temperature sensor can be used for temperature Figure 17 shows the AD7796/AD7797 being used in a weigh compensation of the bridge so the variation of the sensor scale application. The load cell is arranged in a bridge network resistance with temperature drift can be monitored and the and gives a differential output voltage between its OUT+ and conversions from the bridge can be compensated. OUT– terminals. Assuming a 5 V excitation voltage, the full-
VDD AVDD AD7796/AD7797 IN+ REFIN(+) VDD AIN(+) OUT– OUT+ SERIAL DOUT/RDY INTERFACE DIN Σ-Δ AIN(–) MUX ×128 AND ADC SCLK CONTROL IN– LOGIC CS DV TEMP GND INTERNAL DD SENSOR CLOCK REFIN(–) GND CLK
017 06083- Figure 17. Weigh Scales Using the AD7796/AD7797 Rev. B | Page 23 of 24 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