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BQ21040: bq21040

Ian Wang
Mastermind 29740 points
Part Number: BQ21040

Hi Sir,

BQ21040 Vin VS #CHG state

When Vin over 4.45V(4.7V~5.1V change) (Vbat=3.9V)

Why #CHG over 80ms still keep High(Vin over 4.45V )?

When VBAT=3.9V

Thanks,Ian.

  • 0
    TI__Prodigy 460 points

    Hey Ian,

    From my understanding your question is related to the CHG pin behavior. I believe that you are facing a problem with battery detection. If the charger cannot detect the battery then it will never stop being high no matter how much you wait. You can refer to figure 18 on the datasheet, which shows wave forms very similar to what you are experiencing. Do you have a battery simulator? If so can you operate it at a slightly lower or higher voltage? This may solve the problem.

    Please let me know if you have any other questions. 

    Have a good day. 

  • 0 in reply to Manuel Diaz Corrada
    TI__Mastermind 29740 points

    Hi Sir,

    The issue only happen in 3.900 +/- 0.02V

    Others voltage will work fine.

    Do you think if something wrong?

    Thanks, Ian.

  • 0 in reply to Ian Wang
    TI__Prodigy 460 points

    The reason that this problem occurred in that range is because you are quite close to the desired threshold for voltage. If there is additional resistance between the charger and the battery source simulator then the voltage control loop may see the voltage source to actually be 4.2V therefore considering the charge to be done. It is an edge case that would solve itself once the battery discharges a small fraction and the loop notices the problem.