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BQ20Z95 PF Status Bits

Carlo Marsano
Intellectual 1700 points
Other Parts Discussed in Thread: BQ20Z90, BQ29412

Hi Folks,

We are doing a failure analysis into a couple of battery packs.

Looks like there is an issue with spurious tripping of our self-protection fuse.

It would help our investigation if we knew what the reserved bits in the PF Status register of the battery IC signify. We find that the PFIN bit is set and understand this, but we also find that RSVD bit 14 is also set and RSVD bit 13 is not.

Any guidance TI could give on the function of these bits would be greatly appreciated.

The smart battery IC is the bq20z95 v1.50.

Thanks.

  • 0
    TI__Expert 6575 points
    Hi Carlo,
    The definition of BIT14 is as follows:
    RSVD BIT 14: PFVSHUT = 1: Another permanent failure has occurred AND the device attempted to go into shutdown after that event
    RSVD BIT13: SUV— 1 = Safety Under voltage permanent failure
    Please let me know if you have any further questions or comments.
    Regards,
    Swami
  • 0 in reply to Swaminathan Ramanathan75031
    TI__Intellectual 1700 points

    Thanks Swami,

    Can you get us further details on the Cell voltage sense input stages for the BQ20z90 and BQ29412?  

    The datasheet does not mention much, we are looking for possible stray current paths if the thermal fuse opens. 

    If you could provide a detailed input schematic for these inputs (VC1..4), that would be helpful.

    Particularly looking for any bias, pull up/down resistors and protection diodes on these input stages. 

    BQ20z95 pin 39, 40, 41, 42

    BQ29412 pin 4, 6, 7, 8

    Carlo.

  • 0 in reply to Carlo Marsano
    TI__Expert 6575 points
    Hi Carlo,
    I have requested the Design team for this information on the bq20z90, and will be able to get it if it is not proprietary.
    I should have a response tomorrow from them on this.
    I am still tying to track down the designer for the charger part (bq29412) since this is a different group and will let you know what I find.
    Regards,
    Swami