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BQ76952: Disconnecting BAT power input

Theo Hussey51
Prodigy 20 points
Part Number: BQ76952

I would like to be able to rapidly power down the BQ76952, would disconnecting the BAT input be a viable approach, or will the IC source power though ESD diodes on some of the other connections? Something similar to the image below. Would it be better to connect the CP1 capacitor before the MOSFET?

  • 0
    TI__Guru* 77283 points

    Hi Theo,

    This may be possible and it looks like it would not violate any spec abs max conditions, but it is not a graceful approach so we don't recommend this. You would need to be very careful to shut off the FETs before BAT is disconnected and they need enough time for them to turn off (a few ms). 

    There is a Shutdown command with a default delay of zero. Would that meet your needs? There is also the RST_SHUT pin, but it needs to be asserted for 1 second to shut down the device.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 20 points

    Hi Matt,

    Thanks for responding. The aim is to power cycle the BQ76952, so BAT would only be disconnected for a few ms. 
    Is the reason you say to shut off the FETs before disconnecting BAT just to ensure the pack is isolated, or is the part at risk of damage?

    Theo

  • 0 in reply to Theo Hussey51
    TI__Guru* 77283 points

    Hi Theo,

    Is the goal to reset the device. There is a Reset command that will reset all of the registers and Shutdown also accomplishes this.

    The device shuts off the FETs in a controlled way (there will be an app note with waveforms released soon). I'm not sure if cutting the power could risk damaging the FETs.

    Matt