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BQ25703A: supporting Hot Swapping?

Katsu Matsunaga
Expert 7730 points

Part Number: BQ25703A

Hello,

Does this device support Hot swapping?

My customer has an application which is operation to insert and remove the battery with AC adapter powered.

If not, please give me recommended battery charger controller.

Best regards,

Katsu

  • 0
    TI__Mastermind 25800 points

    Hey Katsu,

    While this charger has not be verified in a hotswap scenario, there is likely no issue with hotswapping the battery. As a note, this charger does not automatically detect the presence of a battery. If you are charging and the battery is removed, the charging loop will immediately push itself into the Constant Voltage loop with minimal current. Charging is not terminated. If you suddenly apply a battery, it will re-enter the appropriate phase of charging. However, bear in mind that most hotswap scenarios I've seen involve some transient voltage due to the sudden di/dt, so if this trips some other protection of the charger, it may reset the charging current to 0mA.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    TI__Expert 7730 points

    Hi Joel-san,

    Thank you for your support.

    My customer observes inrush current to battery when BATFET turn on. Do you have any idea to prevent the inrush current?

    Best regards,

    Katsu

  • 0 in reply to Katsu Matsunaga
    TI__Mastermind 25800 points

    Hey Katsu,

    There is not much we can do for inrush current in regards to the BATFET. Keep in mind that the BATFET is a PMOS device with a parasitic body diode in the direction of VSYS. When the battery is applied (with an adapter present), there will be inrush current into both the SYS capacitors and also the BATFET gate drive circuitry.

    You can potentially add a small resistance between /BATDRV and the gate of the PMOS to see if this improves the inrush a bit, but there is no way to remove the inrush into the SYS capacitors. You may also try adding a small resistance between the SYS pin of the charger and the SYS rail where the capacitors sit to further reduce the initial gate drive current draw. However, I am more hesitant about this option and its impact on the controller. These are untested solutions, so you will have to verify their impact in your design.

    Regards,

    Joel H