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BQ76920EVM: BQ76920EVM schematic query.

Star Xu
Genius 9645 points
Part Number: BQ76920EVM
Other Parts Discussed in Thread: BQ78350

Hi

I have a query about BQ76920EVM need your help.

What is the function of Q6? 

Waiting for your reply.

Thanks

Star

  • 0
    TI__Expert 8526 points

    Hi Star,

    Q6 is the pre-charge FET.  This FET is controlled by the PRECHG pin of the BQ78350, and it is connected parallel to the CHG and DSG FETs and in series with a 1kOhm resistor (R48). 

    In order to limit inrush current, the BQ78350 will enable Q6 via the PRECHG pin before the BQ79620 enables the CHG FET via the CHG pin.  The inrush charging current will be directed through Q6 and its series 1kOhm resistor, thus limiting the current.  This prevents high currents from damaging any system components.  After a set delay time, the CHG FET will be enabled and then Q6 will be disabled to limit power dissipation during normal operation.  Hope this helps!

    Best,

    Andria