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UCC21732: LTSpice Simulation Error

Ryan Tran
Prodigy 10 points
Part Number: UCC21732

I keep running into this error during transient analysis. Not sure if its an LTSpice limitation or if my circuit implementation is wrong. If anyone could provide any suggestions, that would help me a lot.

  • +1
    TI__Genius 13460 points

    Hi,

    Welcome to E2E!

    For simulations I would recommend to start with the model of the driver alone before starting to add complexity. I would recommend to do the following steps to first get the simulation running on LTSPICE:

    1. Remove the power switch C3M0120090D, inductor and power source V7 and place a capacitor after the turn on turn off resistor from OUTH/OUTL and COM. This will remove the loading conditions complexity.
    2. Remove the OC detection circuit and short OC to COM to first get the model to switch.
    3. Leave IN- stationary(shorted to GND) first to get the model to switch before feeding differential signals.

    It is hard to pinpoint which portion of the schematic is giving the error by creating and running the whole circuit at once. Please start with making a simple simulation of the driver and start adding complexity while checking functionality at every step to pinpoint the circuit portions causing the errors.

    Best regards,

    Andy Robles

  • +1 in reply to Andy Robles
    Prodigy 10 points

    Hi Alex,

    Thank you for the feedback! After implementing your suggestions, I was able to narrow down the issue to the power switch and OC detection circuit. However, I am still seeing something odd with the RDY and FLT outputs. With OC grounded it should not throw a fault for OC or SC. I also checked for transients at VCC, VDD, VEE for the UVLO condition and found nothing. Attached is my updated circuit and transient simulation.

    Another question regarding loading conditions, what exactly does that mean and how does adding those capacitors in front of turn on/off resistors help with this? Is there anything I can do similar to this that would help with getting the power switch and OC circuit working?

    Edit: Something weird happened to the website which set the issue to resolved, would still like a bit more help though