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BQ76952: BQ76952 Pre-discharge and discharge MOS diode function

Star Xu
Genius 9645 points
Part Number: BQ76952

Hi

The customer design with BQ76952, It appears that the GS pin of the pre-discharge MOS of some machines will have a voltage of 1.5V when pre-discharge is not performed, causing the pre-discharge MOS to turn on.

Remove the zener diode in the red mark form the above picture and it will return to normal (after removal, welding the removed zener diode back will also return to normal).

It is judged that the reverse leakage current of the zener diode slowly increases during use. It becomes larger and causes this situation to occur (use a multimeter to test the Zener diode and it is normal and not damaged);

I would like to know the function of the diode in the red mark， can they be removed?

Another question, how to set the resistance of the components marked in the screenshot？

Waiting for your reply.

Thanks

Star

  • 0
    TI__Mastermind 23730 points

    Hi Star,

    You may try removing the Zener diode or finding a replacement with low enough leakage current to not enable the FET.

    We don't have any strict guideline for how to set the values of the resistors you've indicated. The main considerations when picking the component values is how fast the FETs need to be turned off and at what point do the parasitics become a problem. The Multiple FETs application note explains how these circuits work in more detail.

    Regards,

    Max Verboncoeur