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BQ76952: Difference between normal mode and FET test mode

edgar Wu
Prodigy 30 points
Part Number: BQ76952

Hello TI Team,

I would like to ask if the protection will be maintained under the FET TEST mode?


And what is the difference between FET TEST mode and Nornal mode?

Thanks!

Regards,

Edgar

  • 0
    TI__Guru* 81034 points

    Hi Edgar,

    FET TEST mode is intended for production testing as a way to control FET turn-on and turn-off manually. The protections will still control the FETs while in FET Test mode, but there are multiple differences in the operation. For example the automated control of the pre-charge and charge FETs is not supported (similar for PDSG / DSG). The option to automatically disable the CHG FET during SLEEP mode is not supported. The FET TEST commands are not available in SEALED mode.

    In general, I would not recommend using FET TEST mode in the application. This mode is not fully characterized for application use.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 30 points

    Hi Matt

    Thanks for your answer
    Can you explain "multiple differences in operation" in more depth?
    In your case, FET TEST MODE causes many functions that should be working automatically to disappear, even with the correct settings. Moreover, the design concept of BQ76952 will disappear.
    But other than that, does the control of FET TEST MODE seriously affect the BQ76952?
    For example, conflicting control FETs? Or competing for FET control priority?

    Regards,

    Edgar

  • +1 in reply to edgar Wu
    TI__Guru* 81034 points

    Hi Edgar,

    All of the differences I am aware of from my testing are listed in my last response. Like I said, FET Test Mode was not fully characterized or planned in firmware as a feature to be used in the application, so while it might be possible, the results may not be 100% predictable. 

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 30 points

    When we used the FET TEST mode on the factory side, an operator accidentally triggered an Alert, which caused the AlarmStatus 0x62 to display 0x5082, which is set the bits of SSA and MSK_SFALERT, but when I checked the contents of the SSA register, it was no bit setting.
    Is there any way to restore BQ76952?

  • 0 in reply to edgar Wu
    TI__Guru* 81034 points

    Hi Edgar,

    The SSA register will clear if the fault condition clears, so it may be that the fault condition that was triggered went away. You can clear the bits in the AlarmStatus register by writing to these bits.

    Regards,

    Matt