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ADS1115: why need a OPA333 in the Figre9-6 of datasheet

liu jianyuan
Prodigy 10 points
Part Number: ADS1115

Tool/software:

in my desigh, need to monitor the current shunt.

in order to reduce the circuit, i directly connected the Rshunt to the ADS1115's INX.

is ok ?

becasue the ADS1115's FSR(±0.256V) and LSB(7.8uV) is enough.

and the FSR is form -0.256v to +0.256v, so i no need use the OPA to do level dhift.

  • 0
    TI__Genius 15510 points

    Hello,

    The inputs of the ADC will only accept positive voltages. The full-scale range is shown as ±0.256V due to the input being differential, so it is AINP-AINM. If AINM is higher than AINP, it is a negative result, but both AINP and AINM are still positive voltages relative to ground.

    If you have a bidirectional current you need to measure which will cause a positive and negative voltage drop across the shunt resistor, you would still need to shift the signal to make sure it is positive, and can be read by the inputs to the ADC.

    Regards,
    Joel