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BQ25792: bq25792 can not automatically shut down itself after fully charged

YI HAO
Prodigy 60 points
Part Number: BQ25792

We encountered a problem, when the bq25792 in fast charging state is set before the host is shut down, and a larger charging current is set. Then host is shut down at this time, the bq25792 cannot automatically shut down itself after being fully charged, so the leakage current keep relatively large while system power off because bq25792 still runing.


If we do not make settings before shutdown and use the default charging current, the leakage current is smal after the bq25792 is fully chargedl. The problem is that the charging current cannot meet the design requirements.

 

We want larger charing current for example 2A while system off for short charing time, smaller charging current ( < 1A or even smaller) whlie host is runing depedent on the system temperature.

  • 0
    TI__Guru**** 158961 points

    Hi Yi,

    Are you referring to leakage current into the BAT/BATP pins or VBUS?  

    Note that if the charger's WD timer is enabled, when the host is removed, the charger returns to default settings, which includes charging enabled, ADC disabled and either 1A or 2A charging depending on the PROG pin setting. If the WD timer is disabled, the charger retains that last settings until both VBUS and BAT power are removed.  So, for example, if WD is disable and the ADC is enabled, the charger quiescent current is higher.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 60 points

    Hi Jeff,

    Yes. Thank you for your information.

    Right now, the WD is disabled so the quiescent current is higher. But charging current is what we expect.

    When WD timer is enabled, the maximum timer is only 160s, it won't help. We want host power off charging current up to 2A. But the default charging current is only 1A for 4S battery when the host is removed. The charger returns to default. 

    We cannot set defautl charging current, only IINDPM current.

    Hope the charge full can trigger the charge returns to default setting and shutdown of bq25792.

    best regards,

    YI

  • +1 in reply to YI HAO
    TI__Guru**** 158961 points

    Hi YI,

    Unfortunately, there is no way to prevent the return to default settings when the host is removed and WD timer expires.  Also, the shutdown and ship modes can only be entered via host I2C write when the charger has no power at VBUS.  With VBUS present, the host can also send I2C command to force the charger into HiZ mode, which is the lowest Iq state. 

    Regards,

    Jeff