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PGA302: How do i connect single ended sensor input to bridge based input of PGA302

Arvind
Prodigy 175 points
Part Number: PGA302

Hi there!

Im trying to interface Absolute pressure sensor from bosch ( this part 0 281 002 437 ) as per their datasheet they have recommended this circuit , 

But i am using PGA302 ic in between the sensor output and ADC of MCU , but how do i connect the sensor single output to Bridge based input of PGA302 ic , should i ground the other input? (VINPN) or something else im missing here? kindly help.

  • 0
    TI__Mastermind 31655 points

    Hello,

    The PGAIN input on the PGA302 can take a signal from 0.4V  to 4.38V, so you can ground the VINPN input and connect the pressure output from the sensor to the VINPP as long as you divide down the output a bit to fit in the common mode range. Also note that the ADC takes a differential input, so to make full use of the ADC input range you will need to do a single-ended to differential conversion externally. Otherwise you can just use the positive end of the ADC input at the expense of some resolution.

    The ADC reference is internal, but it is ratiometric to the VDD voltage, so supply the PGA302 VDD with the same supply used for VCC on the pressure sensor.

    Note that if you are using the pressure sensor with included NTC thermistor, you will not be able to use PGA302's internal ITEMP current supply with it. At the lowest output current of 45uA and the NTC's highest resistance of 100k you will have a voltage across the NTC of 4.5V. This is technically within the common mode input range for the TGAIN amplifier, but there is not enough headroom for the current supply. If you intend to use the NTC, it would be safest to use an external current supply.

    Regards,

    Scott