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bq24171 Shutting down while on battery

Michael Rourke
Intellectual 350 points
Other Parts Discussed in Thread: BQ24171

Our application requires us to shut the system down while running on battery.

Is there a way to disconnect the battery on demand while on battery backup?

  • 0
    TI__Expert 3160 points
    Michael,

    Can you help me better understand what you're trying to accomplish?

    It sounds like you would like to turn off the connection from the battery to the system at some point after the adapter is removed (Q3 on the typical application)?

    Thanks,
    Rachel
  • 0 in reply to Rachel Moore
    Intellectual 350 points

    Rachel -

    Our system has no on/off power switch. When the adapter is plugged in, there is power to the system. When the AC power fails, we automatically switch over to battery backup via Q3.

    In order to ship our systems, we'll unplug the adapter and hold a panel switch for a predetermined length of time which will then kill the battery backup.

    It's not clear to me, other then collapsing Vcc to the BQ24171, how to disconnect Q3.

    Hope this helps.

    Mike

  • 0 in reply to Michael Rourke
    TI__Expert 3160 points
    Mike,

    We have this feature in some of our host controlled parts such as the bq29x family, but this isn't a built in feature for the bq24171. Infact, even removing VCC from the device will not disconnect the battery from the system. The p-channel BATFET(Q3) will not be driven to the open state, and the body diode of the FET can also conduct.

    I think you're going to either need an external switch , or some additional circuitry to correctly implement this feature.

    Thanks,
    Rachel