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ADS1120-Q1: As the differential input how to got the negative side when just had one side voltage.

xuejun liu
Prodigy 20 points
Part Number: ADS1120-Q1
Other Parts Discussed in Thread: ADS1120, , ADS131B02-Q1

I want to use the differential input port of ads1120 as the input of both side of the shunt sampling resistor( range ±100mV), but I only have a positive power supply externally. Can it be used if the sampling resistor is in the negative direction, and how can I adjust the PGA according different range of the input. such: when 10mV use 128 gain, 100mV use 16 gain.

  • +1
    TI__Mastermind 20805 points

    Hi Xuejun,

    welcome to our e2e forum and thanks a lot for your interest in our ADS1120-Q1.

    I am assuming you are working on a BMS with a low-side shunt resistor? Means the shunt is connected to the same GND as the ADS1120-Q1?
    When using gains <=4 and disabling the PGA you would be able to measure signals 100mV below GND. If you want to use higher gains then you would have to:

    • use a bipolar analog supply (e.g. +/-2.5V) or
    • use an external amplifier to shift the signal up.

    If you are open to a different device then I would recommend our ADS131B02-Q1 series of ADCs which were developed for this purpose.
    We have 16-bit and 24-bit, as well as 2 channel and 4 channel versions in this family.

    Regards,
    Joachim Wuerker

  • 0 in reply to Joachim Wuerker
    Prodigy 20 points

    Hi Wuerker，

       Sorry for delay reply, kindly thanks for your information.  Yes, we want use more higher gain, and I will check for the ADS131B02-Q1 series specification. If still had some issue need your support, will reached you again. Thanks!

    Regards，

    Liu Xuejun 

  • 0 in reply to xuejun liu
    TI__Mastermind 20805 points

    Hi Liu Xuejun,

    you are very welcome. Just let us know in case you have further questions.
    I will mark this thread as resolved for now.

    Regards,
    Joachim Wuerker