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BQ77PL900: ZEDE Pin

Jacob Olstad
Intellectual 1320 points
Part Number: BQ77PL900

Hi,

Trying to get a better understanding of the operation of the ZEDE pin the datasheet is a little light.

We need to delay the battery pack from providing power when plugged in (will have a gpio to enable pack) the short discription on the ZEDE pin looks like it *may* work but not enough info.

Any other ideas to trick the pack into not starting are welcome.

-Jake

  • 0
    TI__Guru 54715 points
    Hi Jake,
    ZEDE provides 'zero' delay or minimum response to faults, it will not delay operation of the part.
    To delay start up of the bq77PL900 delay the rise of the PACK+ of the system or PACK pin of the IC. Note that pull up of the CHG pin will pull up PACK, so provide adequate circuitry in the design to control the pins while avoiding any stress on the FETs.
  • 0 in reply to WM5295
    TI__Intellectual 1320 points
    Thanks!

    Is there any negatives associated with pulling the pack pin of the IC low?

    Regards,
    Jake
  • 0 in reply to Jacob Olstad
    TI__Guru 54715 points
    Hi Jake,
    The normal concern is that holding PACK low holds CHG low. If the charger is attached so the charge FET source goes high, the circuit which holds PACK low must also break the connection of CHG to the charge FET gate, otherwise the FET is probably on and Vgs could be overstressed.
    The other question or negative with this approach is that it takes power or needs power from an external source. If powered from the battery it adds load, if powered externally it may not work without external power (battery might come on without external power).