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BQ77904: Battery Detection Waveform

Jerry Chu
Genius 4915 points
Part Number: BQ77904

Hi Expert,

If bq77904 got the UV and the charger's battery detection waveform as the below picture, does it any risk to unlock bq77904? Thanks!

  • 0
    TI__Guru* 81034 points
    Hi Jerry,

    What would cause this waveform in the application? This is a very large voltage swing over a short time period.

    The UV detection has a timer for both detection and for recovery. This waveform should not trigger the fault because the voltage is not staying below the UV threshold for the required time. However, I suggest you test this on an EVM to make sure no other faults are triggered by whatever is causing this waveform.

    Best regards,
    Matt
  • 0 in reply to Matt Sunna
    Genius 4915 points
    Hi Matt,
    The waveform is from charger side, the customer added the wrong cap in wrong place. This causes the battery detection waveform to be abnormal. The battery side used BQ77904 for the protect IC. In the first pilot run didn't get the customer fail return and in our experiment, it can unlock the UV battery pack, but we still worry about for all products...
    If you think the waveform has the risk to unlock battery pack, pls let me know it. Thanks!
  • 0 in reply to Jerry Chu
    TI__Guru* 81034 points
    Hi Jerry,

    Are you saying that you did see unlock occur (pack failed) in your experiment? Or am I misunderstanding?

    I worry that there is still some risk especially if the waveform changes from pack to pack. Do they know it will remain consistent?

    Regards,
    Matt
  • 0 in reply to Matt Sunna
    Genius 4915 points
    Hi Matt,
    No, we didn't see unlock occur in our experiment. So, just want to make sure the waveform is ok for bq77904 UV status.
  • 0 in reply to Jerry Chu
    TI__Guru* 81034 points
    Jerry,

    The waveform in the picture should not trigger an UV fault. But I cannot say there is no risk since I don't know if this waveform can change from system to system.

    Matt