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BQ76952: BQ76952 auto unseal issue

Star Xu
Genius 9645 points
Part Number: BQ76952

Hi 

I have a query need your help.

After OTP, lock the chip and SEAL operation, then send the shutdown command to reactivate the battery and find that the chip is automatically unlocked.

After SEAL, the SEC1–SEC0 status is set and turns red. Confirm that the lock is successful. Then click the SHUTDOWN command and wakeup again. It is found that it is automatically unlocked. The SEC1–SEC0 status changes to SEC1:0, SEC0:0.

what is the reason for this? 

Thanks

Star

  • 0
    TI__Mastermind 34630 points

    Hell Star,

    It may be that the OTP was not successful. If it is OTP'd, it should wake sealed.

    Were the steps in Section 3.1 Recommended Steps for Writing OTP, in Production of the BQ769x2 Calibration and OTP Programming Guide application note, followed?

    After writing to OTP and waiting 100-ms, reading from 0x40 would indicate if the OTP was successful.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Genius 9645 points

    Hi Luis

    Thanks for your reply.

    It is confirmed that OTP is successful, the Battery Management Studio software used for OTP is successfully, after reset, the parameters read back are the parameters we burned, which proves that OTP is successful.

    Are there any other possibilities for this phenomenon to occur?

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Expert 4465 points

    Hi Star, 

    Can you confirm the Security:Settings:Security Settings[SEAL] settings are configured to sealed on power-up by default before and after burning the OTP? This bit will determine the power-up SEAL state of the device. Also, there's a limit of how many time you can configure the OTP, so is important to make sure the device can still be OTP before performing the shutdown, another possibility is that the device was not OTP correctly, and some parameters were changed and others not before exceeding the number of signatures. 

    Regards, 

    Arelis G. Guerrero 

    Note: During the US Holidays (Dec 25th till January 2nd) the E2E answers might be delay. Happy Holidays.