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UCC5350-Q1: FMD questions

Yuya Shoji
Expert 5520 points
Part Number: UCC5350-Q1

Tool/software:

Hi team,

I got following questions. Could you support this?

  1. Does the description "OUT" in the table correspond to OUT pin, right?
  2. Could you elaborate the detailed behavior of "OUT level is outside of specified value"?--This information is needed to assess their FuSa management (if this can violate their FuSa goal).
  3. There is no description about VCC1, VCC2, VEE2, IN+, and IN- in the FMD table. Don't the user have to take care of these input pins?

https://www.ti.com/lit/fs/sffs192/sffs192.pdf?ts=1736243831168&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FUCC5350-Q1

Best regards,

Shoji

  • 0
    TI__Mastermind 23206 points

    Hi Yuya,

    1. Yes, OUT in this table corresponds to the OUT pin.

    2. This table was generated based on the percentage of Die area related to each output pin function. In this case, 87% of the die is the output stage transistors. This table states that there is a 29% chance that both the pull-up network and the pull-down network are open, resulting in a floating output of undefined voltage, or closed, resulting in a shorted power supply and a shorted output.

    3. The OUT pin is the only pin that was deemed important for functional safety. In a real design, of course you need to protect the power supply from transient overvoltage and decouple the inputs etc. Functional safety is not based on the use case of the part or likely failure modes based on electrical stresses. It is only based on die area.

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    TI__Expert 5520 points

    Hi Sean,

    Sean Cashin said:
    This table states that there is a 29% chance that both the pull-up network and the pull-down network are open, resulting in a floating output of undefined voltage

    So, "OUT level is outside of specified value" mode corresponds to undefined voltage driving, right?

    Best Regards,

    Shoji

  • +1 in reply to Yuya Shoji
    TI__Mastermind 23206 points

    Hi Shoji,

    Right, that is the determination based on the die area and the available failure modes.

    May I ask how you intend to use this FuSa information? The most likely failure mode is to have both the high-side switch and low-side switch shorted, and the power supply and OUT are tied to ground. This is not reflected by the area-based percentages shown above.

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    TI__Expert 5520 points

    Hi Sean,

    Thank you for your confirmation.

    I don't know how these information exactly are going to be used. But to my knowledge, FuSa engineer typically create some tree diagram and assess either if each mode can violate their FuSa goal or if the mode falls into safe state and its probability.

    Best regards,

    Shoji

  • 0 in reply to Yuya Shoji
    TI__Mastermind 23206 points

    Hi Yuya,

    Thank you for the update. Let me know if you learn more information.

    Best regards,

    Sean