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BQ25883: Sleep Mode or Input Current Disable

Rocko McCombs
Prodigy 105 points
Part Number: BQ25883

Hello,

I would like to know if it's possible to put the BQ25883 in a mode where it does not draw any current on VBUS AND does not draw any current when a voltage is applied to VBUS.

I have the chip in a state where it does not draw any current on VBUS by enabling HIZ. If I remove the voltage on VBUS and re-apply, the voltage is detected and I get a few hundred milliamps of current draw.

I have tried HIZ mode and have experimented with disabling interrupts and mask interrupts.

Once my desired OFF state is reached, I'd like to still be able to draw from the battery to power the load.  Is this mode of operation outside the capability of this chip?

Thanks,

-Rocko

  • 0
    TI__Guru**** 166126 points

    Hi Rocko,

    HiZ bit=0 disabled is the default state.  For HiZ bit=1 enabled to remain after watchdog timeout and VBUS is removed, assuming a battery is attached at BAT, you would have to either continue pinging the Watchdog bit while VBUS is removed or disable the watchdog timer entirely.

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Prodigy 105 points

    Hi Jeff,

    I am disabling the watchdog timer before I set the HiZ bit.

    -Rocko

  • 0
    Prodigy 105 points

    I set the HiZ bit but when I remove and apply VBUS, the Power Good Status bit (PG_GOOD) is set and the HiZ bit is automatically cleared.

    If I could keep HiZ from clearing, I'd be good.  I think maybe this a hardwired response and cannot be prevented.

    -Rocko

  • 0 in reply to Rocko McCombs
    TI__Genius 10385 points

    Rocko,

    What is the status of your ADC_EN when you have HIZ enabled?

    I have observed that when the ADC is enabled, the VBUS unplug/replug will cause the HIZ bit to clear. When the ADC is disabled, the HIZ state will remain active upon adapter unplug/replug.

    Let me know if this helps.

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Prodigy 105 points

    Ricardo,

    Thank you for the suggestion!

    My ADC_EN has been set during all attempts.

    I have now disabled ADC by clearing ADC_EN and it does make a difference. Unfortunately, it does not work every time.

    Sometimes this method fails on the first attempt and sometimes it fails after several cycles of VBUS unplug/replug.  

    Regards,

    -Rocko

  • 0 in reply to Rocko McCombs
    TI__Genius 10385 points

    Rocko,

    Are physically unplugging VBUS or are turning the power supply on/off? I noticed more consistent performance when I physically unplugged VBUS rather than power supply on/off.

    Thanks,

    Ricardo 

  • 0 in reply to Rocko McCombs
    Prodigy 105 points

    Here is a register dump.

    On the left is VBUS plugged in. ADC, Charge, and Interrupts disabled. HiZ enabled. No current draw.

    On the right is after unplug/replug. HiZ has been cleared and current is being drawn.

  • 0 in reply to Ricardo
    Prodigy 105 points

    Ricardo said:

    Are physically unplugging VBUS or are turning the power supply on/off?

    Ricardo,

    Yes, I am physically unplugging VBUS from the supply.

    Regards,

    -Rocko

  • 0 in reply to Rocko McCombs
    TI__Genius 10385 points

    Rocko,

    I understand the ADC enabled/disabled behavior a bit better now. BQ25883 is designed to remain in HIZ until the VBUS voltage rises above VBUS_UVLO_RISING again. The ADC workaround works because the VBUS capacitor can remain charged for longer with the ADC disabled (~800ms). When the ADC is enabled this capacitor almost immediately discharged (~150ms).

    Quickly unplugging and replugging the VBUS with ADC disabled will go unnoticed, but leaving it unplugged for longer periods of time will result in the capacitor being discharged and HIZ being toggled upon replug. This will not work for your application if you want HIZ to remain active indefinitely when VBUS is unplugged.

    I suggest monitoring VBUS and re-enabling HIZ whenever VBUS rises above VBUS_UVLO_RISING (max) in software.

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Prodigy 105 points

    Ricardo said:

    Quickly unplugging and replugging the VBUS with ADC disabled will go unnoticed, but leaving it unplugged for longer periods of time will result in the capacitor being discharged and HIZ being toggled upon replug. This will not work for your application if you want HIZ to remain active indefinitely when VBUS is unplugged.

    Ricardo,

    Thank you, this makes sense now.  That's exactly what I was seeing.  

    I should be able to work around this.

    Kind Regards,

    -Rocko