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BQ76952: Is there any way to change some parameters after the OTP?

Ali Batuhan Demirci
Prodigy 70 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQ76942

Hi Ti experts,

We have a stand alone Custom board so we don't have a host on our board. We did OTP and we want to change some parameters  (like  DATA MEMORY:  CHARGE FET Protections A: SCD), which some of them need to be chage from 1 to 0 or vice / versa.

Is there any way to change some parameters after the OTP?

  • 0
    TI__Guru* 81034 points

    Hi Bathuhan,

    If you can connect to the I2C pins of the device, you can still change parameters. The OTP only changes the default value of the registers, so the registers can still be modified. You can also program OTP more than once, but there is a limit. OTP can only be programmed 8 times total because each time the OTP is programmed a new OTP checksum is written and there are only 8 physical checksum locations available. And you can only change the OTP of a register 2 times practically - a bit can be programmed to '1' for example and then later programmed back to '0', but it cannot be written back to '1' after that.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 70 points

    Hi Matt,

    First of all thank you for your answer,

    Actually  Our card is connected to the battery pack, so I guess  we can not write OTP again (According to "BQ76952, BQ76942 Calibration and OTP Programming Guide" , In order to write to OTP, a voltage between 10 to 12 V should be applied to the BAT pin). 

    Consequently by using external master can we change the  "DATA MEMORY:  CHARGE FET Protections A: SCD"  via I2C with out any hardware modification ? if it works, after successefull modified data, the new modified data will be lost in case of reset / shutdown mode  ?

    Best regards,

    Batuhan

  • +1 in reply to Ali Batuhan Demirci
    TI__Guru* 81034 points

    Hi Batuhan,

    Yes, you can change the register without any hardware modification. However, the modified data will be lost if there is a Shutdown of the device or if the RESET command is sent. 

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 70 points

    Thank you Matt,

    As far as I understand we cannot change parameters permanently without removing it from the battery pack(Our battery-pack voltage is 54,6 V).

    Best regards,

    Batuhan

  • 0 in reply to Ali Batuhan Demirci
    TI__Guru* 81034 points

    Hi Batuhan,

    Yes, that is correct that OTP cannot be changed while it is in the pack since the voltage needs to be between 10-12 V. 

    Best regards,

    Matt