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BQ28Z610: Coulomb counter accuracy

Paul Nossaman24
Prodigy 50 points
Part Number: BQ28Z610

I am wondering about the resolution of measuring the current for the coulomb counter.  We are building a 1S LiPo pack using the bq28z610, our max current/capacity is 1350mA, and we are using a SRN/SRP sense resistor of 10milli-ohm.  If we assume the 16-bit converter with a 3.74uV resolution, would that relate to a 20uA current measuring resolution?  Did I get my calculations right?  Using a 10milli-ohm resistor and only 1350mA max, I realize we are not using the complete Full Scale range of SRN/SRP of +/-100mV.

  • 0
    TI__Guru** 105600 points

    Hello Paul,

    Our gauges use a delta-sigma ADC to calculate current, this architecture is also good for accumulating charge.

    You will need to use the full range to do your calculations for current resolution. If you are trying to measure extremely low current you will also need to configure the deadband current, and the gauge will only report in 1mA increments.

    Sincerely,

    Wyatt Keller 

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Wyatt,

    Thanks for reply, and I do understand a 16-bit delta-sigma is used.  But if my max current is 1350mA and only using a 10milli-ohm resistor, will the resolution be shown in the register as a fraction of 1mA, as the register will show in mAs?  Can you determine what current resolution measurements can be made with my max current and sense resistor?

  • 0 in reply to Paul Nossaman24
    TI__Mastermind 19195 points

    Hi Paul

    The min current would be the 3.74uV / 10 mohm =  .37mA

    Best regards,