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BQ769x0 External Pull-down on CHG

Jessica Riley1
Intellectual 280 points
Other Parts Discussed in Thread: BQ76940

Hello,

I'm considering adding an external pull-down on the CHG output from the BQ76940 chip in order to provide a fast, strong turn-off on the charger FET.  Will this damage the output from the BQ chip, or can the CHG pin be pulled to ground without issue?

Thanks!

Jess

  • 0
    TI__Guru 54715 points
    Generally CHG is expected to have a high resistance to ground or PACK- to reduce load on the battery during normal operation, normal being always on. The datasheet does not list a minimum recommended value, but 1M or larger is typically expected. The pull up resistance when on is 5k typical, current and voltage drop from a load can be estimated. No damage is expected with a reasonable loading but no guidance is provided in the datasheet. The output is not expected to operate near or at a short circuit condition.
    Remember that the charge FET gate must be able to go below ground so you may want to sense the drive voltage and buffer the FET gate drive after the level shift FET.
  • 0 in reply to WM5295
    Intellectual 280 points

    Thank you for your detailed response.  I will avoid shorting the CHG pin to ground.