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BQ27426: Coulomb counting

Martin Jackson
Prodigy 30 points
Part Number: BQ27426

I have a question about exactly how the bq27426 does coulomb counting on the sense resistor. Does it:

Either 1) Measure the voltage across the current sense resistor at some regular interval to work out the current and hence the charge passed?

or 2) Integrate the voltage across the current sense resistor at some regular interval? [This would require some form of internal integrator which would be reset after the ADC has sampled the voltage]

I would hope that the answer is 2) but can't find this in the documentation.

Martin

  • 0
    TI__Mastermind 49361 points

    Hi, Martin,

      The fuel gauge measures current by sensing the voltage across an external sense resistor (10 mΩ, typical). Internally, voltage passes through a gain stage before conversion by the coulomb counter. The current measurement data is available via the AverageCurrent() command.

      In normal mode, the average current flows through the sense resistor and it is updated once per second and is calculated by dividing the 1-second change in coulomb counter data by 1 second. Large current spikes of short duration will be averaged out in this measurement. Units are mA.

    Thanks!

    Phil

     

  • 0 in reply to Phil Yi
    Prodigy 30 points
    Sorry to be thick. Does the coulomb counter integrate the current over the sampling interval? I.e. the fact that the coulomb counter is sampled once per second means that ALL charge is captured?
  • 0 in reply to Martin Jackson
    TI__Mastermind 49361 points

      Yes, all charge is captured by the average current in 1 second sampling interval.

    Thanks!

    Phil