EVAL-AD7797EB datasheet(23/24 Pages) AD

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AD7796/AD7797

Rev. A | Page 23 of 24

APPLICATIONS

The AD7796/AD7797 offer a high resolution analog-to-digital

function. Because the analog-to-digital function is provided by

a Σ-Δ architecture, the parts are more immune to noisy

environments, making them ideal for use in sensor

measurement, and industrial and process-control applications.

WEIGH SCALES

Figure 17 shows the AD7796/AD7797 being used in a weigh

scale application. The load cell is arranged in a bridge network

and gives a differential output voltage between its OUT+ and

OUT– terminals. Assuming a 5 V excitation voltage, the full-

scale output range from the transducer is 10 mV when the

sensitivity is 2 mV/V. The excitation voltage for the bridge can

be used to directly provide the reference for the ADC because

the reference input range includes the supply voltage. This

allows a ratiometric measurement. Therefore, variations of the

excitation voltage do not affect the measurement.

The on-chip temperature sensor can be used for temperature

compensation of the bridge so the variation of the sensor

resistance with temperature drift can be monitored and the

conversions from the bridge can be compensated.

AD7796/AD7797

AIN(+)

AIN(–)

INTERNAL

CLOCK

AVDD

DVDD

REFIN(–)

REFIN(+)

DOUT/RDY

DIN

SCLK

MUX

GND

CLK

Σ-Δ

ADC

VDD

×128

TEMP

SENSOR

SERIAL

INTERFACE

AND

CONTROL

LOGIC

IN+

IN–

OUT–

OUT+

Figure 17. Weigh Scales Using the AD7796/AD7797

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