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BQ21080: Recovery from battery UVLO

Paul Silberschatz
Prodigy 10 points
Part Number: BQ21080

Tool/software:

We are using a 0.5W 5V solar panel connected to the BQ21080 to charge a LiFePO4 battery.  We have programmed a 2.8V Battery Undervoltage LockOut, enabled VinDPM as pseudo MPPT, and 100mA charge current.

In some situations, or battery can be deeply discharged and hit the undervoltage lockout.  Our problem arises when we attempt to recover from this state.  The solar panel does not supply enough current to wake and fully boot our MCU.  It appears that the BQ21080 is resetting all registers to default values as soon as the UVLO is triggered.  This means the battery will only charge at 2mA and needs to reach 3.0V before the battery can supply current to the MCU (which we can trigger with a supervisor on its reset).  

Is there a way to prevent the registers from being reset in the UVLO condition?

  • 0
    TI__Genius 17585 points

    Hi Paul,

    The battery crossing the UVLO threshold condition represents a POR event, essentially the device is turning off and thus non-volatile memory is lost, so there isn't really a way to prevent the register reset from taking place.

    Typically, we recommend the device be placed in ship mode before approaching the UVLO threshold to minimize current consumption and extend battery life as much as possible.

    Best Regards,

    Juan Ospina