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BQ25898: WD issue

Hailiang Zhang
Genius 11120 points
Part Number: BQ25898

Hi 

Could you please help to resolve the problem about BQ25898E？ My customer is asking why the watchdog is turned off and the watchdog overflow error is reported?
According to the datasheet, in host mode, if the WD is turned on, the host needs to feed the dog regularly; if the WD needs to be disabled, the host can disable watchdog timer by setting WATCHDOG bits=00.

The customer disabled WD, but the watchdog timer (WATCHDOG_FAULT bit = 1) is expired appears.
The following is the register status they read back every second. It can be seen that the watchdog is turned off, but the watchdog overflows. And the device does not return to the default mode, and the charging is still going according to the host configuration.

Thanks and best regards

Hailiang

  • 0
    TI__Mastermind 31840 points

    Hi Hailiang,

    When I attempt to recreate the test based on the registers you provide anytime WATCHDOG_FAULT = 1 and I then disable the watchdog timer WATCHDOG_FAULT goes back to 0 to indicate no fault. 

    Considering that you say the device continues to operate according to the host configuration I believe the device is correctly following the I2C write of watchdog timer disable. 

    Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    TI__Genius 11120 points

    Hi Garrett,

    Are you saying that the watchdog has been disabled via I2C?  And after you disabled WD, the WATCHDOG_FAULT bit is 0?
    Also, the engineer said that when they do battery overvoltage test, a 4.5V is applied to BAT, BAT_FAULT becomes 1 and there is an interrupt pulse, but when the overvoltage disappears, BAT_FAULT stays at 1. Do you think this is reasonable? Could you please give your comments?

    Best regards,

    Hailiang

  • 0 in reply to Hailiang Zhang
    TI__Mastermind 31840 points

    Hi Hailiang, 

    Yes the only way to disable the watchdog timer is through I2C. From my observations when WATCHDOG_FAULT bit is initially 1 and then watchdog timer is disabled over I2C WATCHDOG_FAULT = 0 and fault goes away. 

    Hailiang Zhang said:
    but when the overvoltage disappears, BAT_FAULT stays at 1. Do you think this is reasonable?

    I am not able to recreate what the customer is seeing. When I recreate the test scenario every time the battery voltage is reduced below the overvoltage threshold BAT_FAULT returns to 0 the next time I read the registers from the device.   

    Best Regards,

    Garrett