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Original question:

BQ41Z90: BQ41Z90 - MOSFET Failure detection (Stuck close)

BQ41Z90: BQ41Z90 Discharge FET Permanent Fail and PACK pin internal connections

Davide Sarti
Prodigy 70 points

Part Number: BQ41Z90

Hello, 

I'm trying to understand how the Discharge FET Permanent Fail (page 31 on the BQ41Z90 Technical Reference Manual) is triggered. From the manual I see that it's current based. If some current can be pulled when the FET command is OFF, it means there's a FET failure (MOSFET is shorted).

Now, I also see from the BQ41Z90 datasheet that the PACK pin has an internal connection to GND (figure 5-6, page 8); however, I don't understand if this pulling current from the cells' negative or if it's passing through the sensing resistor.

My more generic question is: during normal operation, do we have to implement a circuit that tries to pull current when the MOSFETs are turned OFF (like a MOSFET + resistor driven by our microcontroller) or the BQ is able to try to pull current from the PACK pin? Is there any other suggested solution? 

Please let me know if you need more info or anything is not clear.

Thanks in advance, 

Davide

 

  • 0
    TI__Mastermind 38735 points

    Hello,

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

    Thank you,
    Alan