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BQ25710: Question about VBUS drop

Masayoshi Takahashi
Intellectual 1530 points
Part Number: BQ25710

Hi team,

I got a question of the BQ25710 when the VBUS drop event.

The customer plan to use when VBUS is 12V, Charge voletage is 16.8V (4 cells)

The customer would like to stop the charging when the VBUS is drop such as 10V. Would it be possible to stop the charging?

I think this device can detect the VBUS drop by asserting PROCHOT to CPU but can't stop the charging by self. Is it correct?

Regards,

Yoshi

  • 0
    TI__Mastermind 25800 points

    Hey Yoshi,

    Will you force VBUS to go to 10V or are you hoping to catch VBUS at 10V if the 12V adapter/power supply is overloaded?

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    TI__Intellectual 1530 points

    Hi Joel,

    Thanks for your comment.

    The customer hope  to catch VBUS at 10V if the 12V adapter/power supply is overloaded.

    Regards,

    Yoshi

  • 0 in reply to Masayoshi Takahashi
    TI__Mastermind 25800 points

    Hey Yoshi,

    The charger comes with a feature called VINDPM in order to perform the function you are requesting.

    When the input voltage drops below a programmable threshold (by default, the threshold is VBUS(unloaded) - 1.28V), the charger will gradually reduce the charging current to maintain the system load.

    This can be programmed via the Input Voltage register.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    TI__Intellectual 1530 points

    Hi Joel,

    Thanks for your answer. I understood DPM function can be reduce the output current.

    The customer would like to stop the charging when VBUS is drop.

    I think they have 2 solution to stop the charging as below. Could you tell me whether each solution can work or not?

    1. After the PROCHOT signal is detected by MCU, Host MCU can be stop the device.

    2. Adding comparator on VBUS by divided resitor to detect voltage drop on VBUS. 

    Regards,

    Yoshi 

  • 0 in reply to Masayoshi Takahashi
    TI__Mastermind 25800 points

    Hey Yoshi,

    Understood. 

    For 1) When VBUS drops to 12V, you will need to enable the LOWER_PROCHOT_VDPM bit in order to use the same VINDPM value as the /PROCHOT trigger. You may leave the bit as is if you feel VBUS will collapse further than 12V. From here, you can use your MCU to disable charge.

    2) The charger comes with an integrated comparator. If you want to disable the entire converter (not just the charging path), consider using a resistor divider from VBUS to the CMPIN pin, and set the FORCE_LATCHOFF bit which will disable the entire converter when the internal comparator is triggered. 

    Regards,

    Joel H