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BQ27421-G1: Learning question

Allan Fan
Expert 6710 points
Part Number: BQ27421-G1
Other Parts Discussed in Thread: BQ24296

Hi Export,

Customer would use gauge BQ27421-G1 + charger BQ24296. Simple schematic block is like below. Would you please confirm the connection is correct if the pack would be removable? Can BIN pulldown resistor also connect to the T pin from the battery pack?

Second question is about the temperature measurement and learning. BQ27421-G1 don't need to do learning cycle to get golden image, but how frequently host need to write temperature value into the gauge for accurate RSOC update?  

Thanks,

Allan

  • 0
    TI__Guru 52115 points

    This question has been assigned to our engineer and we will get back to you.

    Andy

  • 0
    TI__Guru 56146 points

    The sketch looks good from a gauge perspective.

    Sharing the "T"hermistor pin from the pack with the charger is problematic as both the charger and the gauge rely on accurate biasing for temperature measurements. Even if you disable temperature measurements in the gauge, the gauge may still interfere with the charger thermistor bias.

    If you use host written temperature for the gauge, you must make sure that the host writes the temperature often enough that the gauge doesn't miss any changes in measured temperature. The gauge runs on a 1 second cycle so this doesn't have to be more often than once a second. It's not possible to give you a maximum interval as this depends on how dynamic the temperature changes are in your system.