The subject says it all.
My setup is a ADS1291 with an INA333 as an amplifier for the signal of a 350Ohm strain gauge bridge.
Did some mistake on my Breadboard and was hunting it the whole afternoon. The converted signal was way smaller than expected measured with the scope. So that is the point where I ask myself what else is going on besides INP-INN.
Thanks in advance.
Philipp
Hello Philipp,
From the ADS1291's perspective, it does not make a difference whether you fix the INP or the INN input to a CM voltage. The ADC will still convert the differential voltage into a digital output code, as long as this differential voltage x PGA gain is less than +/- Vref. Refer to the figure below:
Single-ended usually implies that one input is tied to AVSS. I would recommend tying the fixed CM voltage to mid-supply in order to allow your input signal to swing above and below the CM voltage without exceeding the PGA supplies. The second input should also be given the same mid-supply DC bias such that the PGA is only gaining the differential signal that you are interested in.
Best Regards,
