AD7710 datasheet(27/28 Pages) AD

27 / 28 page

AD7710

REV. F

–27–

APPLICATIONS

Figure 20 shows a strain gage interfaced directly to one of the

analog input channels of the AD7710. The differential inputs to

the AD7710 are connected directly to the bridge network of the

strain gage. In the diagram shown, the on-chip reference of the

AD7710 provides the voltage for the bridge network and also

provides the reference voltage for the AD7710. An alternative

scheme, outlined in Figure 21, shows the analog positive supply

voltage powering the bridge network and the AD7710 with the

CLOCK

GENERATION

SERIAL INTERFACE

CONTROL

OUTPUT

CHARGE-BALANCING A/D

CONVERTER

DIGITAL

FILTER

AD7710

PGA

AGND

DGND

MODE SDATA SCLK

MCLK

OUT

MCLK

AIN1(+)

AIN1(–)

REF

IN (–)

REF

IN (+)

SYNC

A = 1 – 128

DRDY

TFS

RFS

AIN2(+)

AIN2(–)

VSS

VBIAS

AVDD

DVDD

2.5V

REFERENCE

REF

OUT

ANALOG

+5V SUPPLY

ACTIVE

GAGE

DUMMY

GAGE

AUTO-ZEROED

MODULATOR

Figure 20. Strain-Gage Application with the AD7710

CLOCK

GENERATION

SERIAL INTERFACE

CONTROL

OUTPUT

CHARGE-BALANCING A/D

CONVERTER

AUTO-ZEROED

MODULATOR

DIGITAL

FILTER

AD7710

PGA

AGND

DGND

MODE SDATA SCLK

MCLK

OUT

MCLK

AIN1(+)

AIN1(–)

SYNC

A = 1 – 128

DRDY

TFS

RFS

AIN2(+)

AIN2(–)

VSS

VBIAS

AVDD

DVDD

2.5V

REFERENCE

ACTIVE

GAGE

DUMMY

GAGE

DIGITAL

+5V SUPPLY

ANALOG SUPPLY

EXCITATION

CURRENT

REF IN(+)

R =

VREF

IEXCITATION

REF IN(–)

REF

OUT

Figure 21. Alternate Scheme for Generating AD7710 Reference Voltage

reference voltage for the AD7710 generated across a resistor

which is placed in series with the bridge network. In this case,

the value of the reference resistor is determined by the required

reference voltage divided by the value of the excitation current.

The on-chip PGA allows the AD7710 to handle an analog input

voltage range as low as 20 mV full scale. The differential inputs

of the part allow this analog input range to have an absolute

value anywhere between VSS and AVDD.

AD7710 Datasheet(PDF) 27 Page - Analog Devices

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