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BQ25750: BQ25750: Adapter does not power system after battery deep discharge until battery removed

Rushikesh Paradeshi
Prodigy 60 points
Part Number: BQ25750

Tool/software:

Hello,

I am using the BQ25750 charger IC in my design with a 7-cell Li-ion battery pack. I have observed the following behavior:

  1. When the battery is deeply discharged and input power (adapter) is not connected, the system shuts down as expected.

  2. Then, when I plug in the adapter (without removing the battery), the system does not power on.

  3. However, if I remove the battery and plug in the adapter again, the system powers on properly.

Is this expected behavior?
Why does the system not power up from the adapter when the deeply discharged battery is still connected?
Is there any register or configuration that I should adjust in the BQ25750 to allow the system to power up directly from the adapter even if the battery is deeply discharged?

Any guidance on how to handle this scenario would be appreciated.

Thanks!

  • 0
    TI__Mastermind 30915 points

    Hello Rushikesh,

    Thanks for being patient with this. We are busy at the moment and we will get back to your question later this week.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    TI__Mastermind 30915 points

    Hello Rushikesh,

    Rushikesh Paradeshi said:
    Is this expected behavior?

    I don't think this is expected behavior.

    Rushikesh Paradeshi said:
    Why does the system not power up from the adapter when the deeply discharged battery is still connected?
    Is there any register or configuration that I should adjust in the BQ25750 to allow the system to power up directly from the adapter even if the battery is deeply discharged?

    I have a few questions to help us debug this:

    • For this test, can you tell me what the battery voltage and VAC voltage is here?
    • Do you have a system load also applied to the BQ25750?
    • Can you read the registers of the BQ25750 and see if any status or flag registers are being set?
    • Can you use an oscilloscope to measure the voltage on ACDRV, BATDRV, and VSYS to see what these pins are doing?
    • Does setting the CE pin HIGH and then setting the CE pin LOW cause the BQ25750 to start charging again?

    Best Regards,
    Ethan Galloway