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BQ27742-G1: BQ27742-G1 Protection Checksum

Star Xu
Genius 9645 points
Part Number: BQ27742-G1
Other Parts Discussed in Thread: BQSTUDIO

Hi

The customer want to change OC and OV protection, but after change the MOS turn.

Change the Protection Checksum to  0000 , 7FFF, but failure.

Attached the figure and gg file for your reference.

gg and figure.zip

Another query is when the DSG MOS is turn off, the pack still have the output voltage.

Please help check the schematic.

TP01S031.pdf

Thanks

Star

  • 0
    TI__Guru** 105760 points

    Hello Star,

    The checksum error is within bqStudio? The error will show when the expected values don't match what is programmed, are you sure the gauge's memory updated when you programmed the new protection settings? You can check by refreshing the DF after you change the values.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Genius 9645 points

    Hi Wyatt Keller

    Thanks for your reply.

    Attached the Screenshot for detail 

    bqStudio.xlsx

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Guru** 105760 points

    Hello Star,

    The DSG bit in flags() only indicates if the gauge is in discharge mode, if they had just calibrated the gauge CC then it will be high until the timeout.

    The checksum of the new protection config must be updated in the gauge DF, you can check the TRM:

    4.1.1.18 PROTECTOR_CHKSUM: 0x001A Instructs the fuel gauge to calculate protector checksum as a 16-bit unsigned integer sum of Prot OV Cfg and Prot OC Cfg excluding device specific variables. The most significant bit (MSB) of the checksum is masked yielding a 15-bit checksum. This checksum is compared with value stored in the data flash Prot Checksum. If the value matches, the MSB is cleared to indicate pass. If it does not match, the MSB is set to indicate failure. The checksum can verify the integrity of the protector configuration.

    NOTE: The fuel gauge will disable the CHG and DSG FETs while the programmed Prot Checksum is invalid (that is, does not match the computed checksum). This protects against safety events due to accidental protector misconfiguration.

    Sincerely,

    Wyatt Keller