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BQ24780S: BQ24781 might drain current from battery in AC mode when the battery is fully charged

Frank Chang
Prodigy 10 points
Part Number: BQ24780S
Other Parts Discussed in Thread: BQ24781

In our system, when AC adapter is plugged in and the battery is fully charged (100%) in idle mode, we can see current flows through R625 from the battery which causes battery capacitoy down to 99% after 12 hours.

If we remove R636,R643 and L15, there will be no current measured on R625.

Is this a normal behavior for BQ24781?

  • 0
    TI__Genius 11385 points

    HI Frank,

    It could be due to the IQ of the IC. It is normal. 

    The "QUIESCENT CURRENT" section of the datasheet has more information about the amount of IQ that you can expect.

    Thanks,

    Peng

  • 0
    Prodigy 10 points

    Hi Peng,

    I checked the spec of BQ24781, there is no information shows the quiesent current in adapter+battery mode, do you have any document to show that?

  • 0 in reply to Frank Chang
    TI__Genius 11385 points

    Hi Frank,

    When the adapter and battery is both present, the power consumed by the IC is usually not important (hence not on the datasheet) because you can always enable charge to charge the battery up.

    Thanks,

    Peng