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BQ24800: Watchdog

Far Hung
Expert 7010 points
Part Number: BQ24800

Hi Expert,

My customer want to know what is the propose for the watchdog feature? And how do I know if the bq24800 trigger watchdog function? Any register will indicate it?

Far

  • 0
    TI__Mastermind 30372 points

    Hi Far, 

    Thank you for reaching out!

    The BQ24800 device includes a watchdog timer to suspend charging, hybrid power boost mode or battery only boost mode if the charger does not receive a write ChargeVoltage() or write ChargeCurrent() command within a certain amount of time (175 s for example). The timer can be adjusted or disabled in REG0X12 [14:13]. 

    Please see sections 7.3.8.1 and 7.6.2.1 in the datasheet for more information. 

    Best Regards, 

    Aya Khedr 

  • 0 in reply to Aya Khedr
    TI__Expert 7010 points

    Hi Aya Khedr,

    Yes, I know the feature of watchdog, but I assume my customer wants to know more about the purpose of watchdog. Like why the WD will disable the hybrid boost mode? Does it want to prevent charger running on hybrid for too long time? And why WD reference the charge voltage/ current to decide weather to entry WD mode?

    Far

  • 0 in reply to Far Hung
    TI__Mastermind 30372 points

    Hi Far, 

    The watchdog timer is a safety feature in the case when the host processor stops communicating. If it doesn't communicate within a certain amount of time, the charger's registers are reset to default values.

    The implementation of the WD timer is not to prevent the charger from running on hybrid-mode for too long; it is only to ensure that the device is receiving commands and is able to communicate. 

    I hope that makes sense. Please let me know if you have additional questions. 

    Best Regards,

    Aya Khedr 

  • 0 in reply to Aya Khedr
    TI__Expert 7010 points

    Hi Aya Khedr,

    According datasheet mention, "if the charger does not receive a write ChargeVoltage() or write ChargeCurrent() command within
    175 s". I know if the ChargeVoltage/ current is 0 and exceed 175s, charger will entry WD mode. How about the     ChargeVoltage/ current is not 0 and exceed 175s, is charger will entry WD mode as well?

    Far

  • 0 in reply to Far Hung
    TI__Mastermind 30372 points

    Hi Far, 

    Yes, that is correct. If the charger does not receive any commands within 175 s, it will reset those values to default conditions. Once again, the WD timer can be disabled and it would no longer reset to default conditions unless the charger is power cycled. This feature can be seen on the BQ24800 EVM as well. 

    Best Regards, 

    Aya Khedr