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UCC21710-Q1: PSPICE model not matching expected behaviour during OC fault

Marcus Vencel
Prodigy 40 points
Part Number: UCC21710-Q1
Other Parts Discussed in Thread: UCC21710, UCC21732


I am trying to simulate an overcurrent fault to verify the desat circuit that is suggested in the datasheet. However, I am experiencing a longer delay between fault and turn off than expected, around 3us as seen in the plot below.

Is this expected behaviour?

The circuit looks like below. The UCC21710 model imports to PSPICE as a UCC21732 symbol (hence the CLAMPE and not CLAMPI) but the SPICE model says UCC21710.

  • 0
    TI__Expert 4875 points

    Hi Marcus,

    I'm sorry you are having some troubles. Can you please try attaching your images in a different format? They are not showing up for me.

    Thank you,

    Audrey

  • 0 in reply to Audrey Dearien7
    Prodigy 40 points

    Hello,

    I hope this works. They show up quite big on my screen and I can't figure out how to make them smaller in the editor.

  • 0 in reply to Marcus Vencel
    TI__Expert 4875 points

    Hi Marcus,

    Thank you, I can see your images now.

    The simulation waveforms look like UCC21732 because it has activated 2LTO. You are correct that the 2LTO duration should be 1ms or less as specified in the datasheet. Please give me a chance to look into the simulation. 

    Regarding the UCC21710 circuit, I do see the same issue that the model symbol is named as UCC21732. However, in my simulation the correct .lib file for UCC21710 is called, so STO is initiated at OC.

    Are you hoping to use UCC21710 in your simulation? If so, I think that maybe the wrong lib file is being called resulting in the 2LTO operation you show in the waveform.

    Regards,

    Audrey

  • 0 in reply to Audrey Dearien7
    Prodigy 40 points

    Hello Audrey,

    I ran the transient simulation that was included with the UCC21710 model and can see that the model works. Did some modifications as well to match 10u periods and added the same MOSFET that I use and it still works and it turns of within 1us after OC is triggered. This makes me believe that there is something wrong with my own schematic and simulation so I will look into that once more and see what could be wrong.

    Regards,

    Marcus

  • 0 in reply to Marcus Vencel
    Prodigy 40 points

    Hello again,

    I added the library different this time, and added the .olb file directly to the library tree instead of adding it under Edit Simulation Profile/Configuration files. This made the simulation work as intended, so I think it is solved.

    Thank you for your help,

    Marcus

  • 0 in reply to Marcus Vencel
    TI__Guru**** 189401 points
    Hi, Marcus, That is great news! Thank you very much for letting us know how you solved the issue. Let us know if you run into any further issues.