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BQ27421EVM-G1B: Coulomb Counting Min Current And Deadband

Nathan Tennies
Prodigy 140 points
Part Number: BQ27421EVM-G1B

I know the BQ24721-G1B supports a Current Deadband threshold; Average Current will report 0 for any average currents that are below this threshold. I also know that some of your fuel guages also support a Coulomb Counter Deadband, which is used to exclude current measurements that fall below this threshold for inclusion in coulomb counting. Questions:

  • Does the BQ24721-G1B have a configurable Coulomb Counter Deadband? I don't see one listed in the Technical Reference.
  • If not, does the BQ24721-G1B have a hardcoded Coulomb Counter Deadband? And, if so, what is it?
  • If not, given the integrated 7 mΩ sense resistor, what is the minimum current that can be counted by the BQ24721-G1B Coulomb Counter via the integrating ADC?

  • 0
    TI__Mastermind 19195 points

    Hi Nathan,

    The deadband available is the one listed in TRM.

    All the characteristics of the coulomb counter are listed in the data sheet. You can evaluate the cc accuracy across different currents after calibration

    Best regards,

  • 0 in reply to Nick Brylski
    Prodigy 140 points

    Nick,

    Thank you for your response but you didn't actually answer any of my questions, which is surprising since these all seem like they should be pretty straightforward. BTW, I should mention that we're actually using the BQ27421-G1B on a custom board, not the EVM (apparently I chose the wrong thing in the popup menu), if that matters.

    >The deadband available is the one listed in TRM

    The Deadband described in the TRM applies to the Average Current measurements. My question has to do with whether there is a also deadband that applies to the Coulomb Counter.

    Are you suggesting that this Current Deadband is also applied to the currents measured by the Coulomb Counter? In other words, if the Deadband threshold is set to 5 mA, as it is by default, then are you saying that no currents under 5 mA are measured by the Coulomb Counter?

    If that is not what you are saying, my next question is whether there is a separate deadband that applies to the current measurements used by the Coulomb Counter? If so, what is that deadband and can it be configured?

    > All the characteristics of the coulomb counter are listed in the data sheet. You can evaluate the cc accuracy across different currents after calibration

    The datasheet does not specify the minimum current that can be incorporated by the Coulomb Counter. It specifies 16 bit resolution, but without knowing the reference voltage used by the integrating ADC, it's not possible to independently calculate the minimum current available to the Coulomb Counter. Can you supply that.

    Is there a reason you can't supply this basic piece of information about the operation of the part?