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BQ41Z90: BQ41Z90 - MOSFET Failure detection (Stuck close)

Davide Sarti
Prodigy 70 points

Part Number: BQ41Z90

Hello,

I'd like to implement a failure detection on a BMS; specifically, I'd like to trigger a permanent failure error whenever the charge or discharge MOSFETs are stuck close - in case of discharge, I want the permanent failure to be triggered if the DSG MOSFETs are driven OFF and if the current is still greater than a certain threshold.

On the reference manual (page 288) I see it is possible firmware-wise; from an hardware standpoint, do I have to add a small external discharge circuit to try to sink current when the MOSFETs are driven OFF or can I use an embedded hardware in the IC (for instance in the PACK pin), that pulls down the line whenever the MOSs are OFF?

 

Thanks in advance,

Davide

  • 0
    TI__Mastermind 38795 points

    Hello,

    This question has been assigned within the team and will be reviewed and followed up with a application engineer when possible. In the meantime please attach any associated .log/.gg files associated with the projects

    Thank you,
    Alan 

  • 0 in reply to Alan Frias
    TI__Mastermind 31845 points

    Hi,

    Sorry, I am confused on the questions. 

    What do expect to cause the FETs to get stuck on?

    The Gauge will stop driving the FETs if a protection event is detected. When would you classify the FETs as stuck on?

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 70 points

    Hi,

    The condition I'm referring to is when a MOSFET fails and drain-source get short circuited. In this case, if I have many MOSFETs in parallel, the event is detectable when the MOSFETs are driven OFF and either:

    • A voltage is still detected at the output;
    • A current is still flowing;

    In these conditions, it means that a MOSFET is short circuited and I'd like a permanent failure to be triggered.

    I was wondering if this kind of event can be detected by the BQ and, if yes, if a pull-down circuit is necessary to try to pull current from the cells.

    Best regards,

    Davide

  • 0
    Prodigy 70 points

    Hello Diego, I see that the MOSFET failure detection could be done by pulling from the PACK pin when the MOSFETs are driven open; in this case, if a MOSFET is shorted some current will be pulled, detected and a permanent failure triggered. Do you confirm this is possible and known as a method to detect a stuck close MOSFET? Thanks!