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BQ27742-G1: which mode is the device in after a power is connected to it?

mike zhang
Intellectual 925 points
Part Number: BQ27742-G1

Hi,

we are using the device and want to know what mode the device is in after connecting a power or battery to it? based on the spec, it probably is in the analog shutdown mode, isn't it?

we know that in this case the CHG/DSG FETs are OFF. in order to turn them ON, a charger has to be attached after connecting a power.

But in our application battery may be disconnected momentarily and requires recovery without charger involved. we wonder that there is a way to turn the FETs ON without a charger attached to after applying a power?

Thanks!

Mike

  • 0
    TI__Mastermind 34775 points
    Hi Mike,

    bq27742-G1 powers up when the battery is connected with the DSG and CHG FETs open and requires a charger to be connected to close the FETs. You can add manual push button circuitry to momentarily short BAT+ voltage to PACK+ for the gauge close the FETs when the battery is connected, but care must be taken to limit current in case of a short on the PACK terminals.

    bq27742-G1 was intended to be used as a pack-side gauge. It sounds like you trying to use it as a system-side gauge, is that correct?
  • 0 in reply to Damian Lewis
    Intellectual 925 points

    Thanks Damian!

    In our application the device is not built in battery pack and battery may be lost its connection momentarily in some worst cases, and then re-connected automatically. How we can restore the power without applying a charger in this case? For instance, change some settings or registers to allow the FETs turned ON when powered up? If it can't be done by changing settings or registers, will the device still work if bypassing the FETs (short as always ON)? We know the bypassing will lose all protection functions but this may be OK to our application (we have other protection layers).

    Mike

  • 0 in reply to mike zhang
    Intellectual 925 points

    Hi, can someone answer my questions above? we really need a solution on this. thanks!

    MIke

  • 0 in reply to mike zhang
    TI__Mastermind 34775 points

    Hi Mike,

    What you mentioned is a system-side gauge type application. bq27742-G1 is for pack-side application where the battery/cell is always connected to the gauge. Unfortunately, the way the protection features were designed for bq27742-G1 there's no bypass of the FETs. If your application have instances where the gauge is disconnected from the battery/cell and you can connected a charger each time, you will have to design some circuitry to momentarily bypass the CHG and DSG FETs when reconnection of the battery occurs.