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BQ24157: BQ24157: Does not automatically enter into High-Z mode

Abbas Mehdi
Intellectual 580 points
Part Number: BQ24157

Hi.

We are performing some tests on the BQ24157, and observed that, contrary to the datasheet, it does not automatically enter into high impedance mode upon VBUS<VUVLO, rather continuously reports a fault for the same (011-Bad Adaptor or VBUS<VUVLO). We don't want such a behaviour. We want the device to be all quite like a sleeping baby when it is not in use.

Is there a way to achieve that?

Looking forward to hearing back soon.

Warm regards,

Abbas Mehdi.

  • 0
    TI__Guru**** 163446 points

    Hi Abbas,

    The charger is HiZ mode when VBUS<UVLO.  The high Z mode register bit or CD pin=1 is only required to enter HiZ when VBUS>UVLO.

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Intellectual 580 points

    Hello Jeff.

    Thank you for responding to my question.

    Yes, that is what the datasheet states, and that is pricesly what I am trying to ask. The charger is not entering HiZ when VBUS<UVLO on its own.

    Looking forward to hearing back from you soon.

    Warm regards,

    Abbas Mehdi.

  • 0 in reply to Abbas Mehdi
    TI__Guru**** 163446 points

    Hi Abbas,

    Why do you think the charger is not in HiZ?  There only 3 operating states: HiZ, charge and OTG.  If voltage at VBUS is < UVLO, then the charger cannot be in charge mode.  If OTG bit and pin is not enabled and VBUS < 5V, then the charger is not in OTG mode.  That leaves HiZ.  With no load attached to the battery, how much current is the charger sinking?  Per the 3rd line item in the electrical spec table on d/s page 7, the max current into IC should be less than 23 uA in HiZ mode.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 580 points

    Hello Jeff.

    Yes, it is true that the device has only 3 operating modes, and when it is neither charging nor boosting, it has to be in HiZ mode. By monitoring the current, it seems the device does enter into the HiZ mode. It's just that the device was consistently issuing fault pulses, as mentioned in the original post, that I thought it is not entering into the HiZ mode. However, when I checked it on another board we had, the behavior was not very different from is mentioned in the datasheet.

    Do you have any idea what might be the cause of that faulty behaviour in the first board?

    Warm regards,

    Abbas Mehdi.