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BQ20Z65-R1: PFSTATUS 4000:0000 on bq20z65-R1

Jeffrey Chase
Intellectual 510 points
Part Number: BQ20Z65-R1

I have a battery that was returned from our customer for a failure analysis that was in a permanent fail state. The PF Status bytes were 4000 and 0000. The GUI for the evaluation states that this is reserved bit, but the bq20z65-R1 tech reference states that the bit indicates the battery shutdown after another PF bit was set (PFVSHUT.)

First, which is the correct definition of that status bit.

Second, if the bit is a reserved bit, what does it mean if it is set. If it is PFVSHUT, what conditions could cause that bit to be set with no other PF bits set in either PF Status register?

  • 0
    Intellectual 510 points

    Reviewed the PFStatus1 information for the bq20z65-R1 again and realized that the PFVSHUT bit referenced before was actually under Saved PF Flags 1. If I am understanding this correctly, this bit gets set when a PF flag has been set, then the battery goes into shutdown. Does that mean the RSVD bit in the PFStatus1 is set when PFVSHUT is set in PF Flags 1?

    If that is the case, then I now have two batteries that have been returned with this bit set in PFStatus and PF Flags 1 with no other bits set. In both cases, the batteries were drained with cell voltages low enough to put the battery in CUV under Safety Status. Could this be what is causing the PFVSHUT bit to be set?

    Again, the battery came back with PFStatus1 at 4000 and PFStatus2 at 0000, with PF Saved Flags 1 and 2 reading the same. Trying to understand this properly so it can be explained to the customer. Any help in understanding this would be greatly appreciated.

  • 0 in reply to Jeffrey Chase
    TI__Expert 6575 points

    Hi Jeffrey,

    Your hypothesis is correct. It looks like the voltage is dropping very quickly and once it goes below the "Flash Update OK voltage" setting, it will not update the PF Flags anymore or record any of the other conditions.

    If the  "Flash Update OK voltage" is set to a value above 3500mV, you can increase this value so that you have a better chance of recording the details of the event in the future.

    Swami