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BQ25895: Can I use \QON pin for hardware reset?

Part Number: BQ25895

Hello TI experts,

My customer considers BQ25895 for their new product now.

and they want to reset this IC if it does not work properly.

In the datasheet, I found the description about \QON pin.

"When VBUS is not plugged-in, a logic low of tQON_RST (typical 10sec) duration resets SYS (system power) by
turning BATFET off for tBATFET_RST (typical 0.3sec) and then re-enable BATFET to provide full system power
reset."

it seems that when I insert low signal for 10 second on \QON pin, BATFET will be turned off like shipping mode,

and insert low signal again for 1 second on \QON pin, BATFET will be turned on and it would work normally.

Please check it whether I am right or not. Thanks.

Best regards,

Chase

  • Hi Chase, 

    The system reset function triggered by driving /QON pin low will only occur when no Vbus (input adapter) is present. It is described in detail in section 8.2.10.3 of the datasheet on page 26.

    All that is needed to initiate the system reset is drive /QON logic low for t_QON_RST (18 second max). The BATFET Q4 will turn off, hence disconnecting power to system load, then turn back on after a short time on its own. The reset feature is automatically enabled, but can be disabled if BATFET_RST_EN = 0 on REG09. 

    Best Regards,

    Garrett 

  • Dear Garrett,

    Thank you for your support.

    1. I understood that system reset function would occur with no VBUS situation. -> it means that if I have a trouble when I charge the device with adapter(VBUS input) then I detach the adapter and input low signal to \QON. so I can reset BQ25895. am I right?

    2. if no.1 is right, should I input low signal to \QON again to activate BQ25895?

    3. is there any minimum time for system reset, input low signal to \QON? (there is only maximum time, 18 second.)

    Best regards,

    Chase

  • Hi Chase, 

    1) Correct, to do a full reset you would want to remove adapter then drive /QON low for T_QON_RST. 

    2) No, if using /QON for system reset function you do not need to drive low to activate bq25895. The device will turn back on on its own. /QON pin happens to also be used to activate device out of ship mode, which is a different function to the hardware reset you ask about. 

    3) The datasheet states the minimum time requirement on the input low signal to /QON to enable reset is 12 seconds and maximum 18 seconds.

    Best Regards,

    Garrett 

  • Dear Garrett,

    Thank you for your support. I will discuss it with my customer and post another thread if I have a question.

    Best regards,

    Chase