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Original question:

TPS3850: [TPS3850]Usage in Safety Applications

TPS3850: TPS3850 in safety application

AHashem
Intellectual 270 points
Part Number: TPS3850
Other Parts Discussed in Thread: , TMS320F2800157

Tool/software:

In a previous thread, I inquired about the ASIL rating of the TPS3850, and the response was as follows: "The TPS3850-Q1 is not an ASIL rated device. However, we do have functional safety information (FIT, FMD, & FMA) that can be used by the functional safety assessor to perform system level ASIL calculations."

For my current project, which is targeting ASIL B, we have disabled the internal watchdog for the TMS320F2800157. My thought is that enabling the internal watchdog and supporting it with the external watchdog (TPS3850) might suffice to meet the ASIL B requirements for this project.

Do you have any thoughts or recommendations regarding this approach? Specifically, are there any considerations or additional steps we should take to ensure that this configuration will adequately cover the ASIL B requirements?

Thanks,

  • 0
    TI__Genius 11490 points

    Hi Ahashem,

    Having the external window watchdog with its own independent clock and power path to monitor the processor is typical practice to meet ASIL B at a system level. By also enabling the internal watchdog you just make the system more robust. I would like to add that you also typically need to implement a method to test the external watchdog to ensure that it is still working properly. This can be done as simply as providing the incorrect window timing and testing whether the output transitions as expected.

    Thanks,
    Joshua

  • 0 in reply to Joshua Garcia
    Intellectual 270 points

    Thanks, Joshua for the answer, 

    Do you have proof that having the external watchdog will be sufficient for ASILB

  • 0 in reply to AHashem
    TI__Genius 11490 points

    Hi Ahashem,

    The only way to prove ASIL-B compliance is to do a complete system level FuSa breakdown calculation.

    Thanks,
    Joshua