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TINA/Spice/THS3091: strange Transient simulation results

Bruno Torremans
Prodigy 10 points
Part Number: THS3091
Other Parts Discussed in Thread: TINA-TI

Tool/software: TINA-TI or Spice Models

Hello, we get the following strange Transient response with the TINA-TI Reference Design :

  • 0
    TI__Mastermind 40295 points

    Bruno,

    I suspect the simulation step size is too big at the output waveform edges.

    In an active TINA session with the reference circuit, please select Analysis/Set Analysis Parameters.
    Click the finger icon on the lower right corner of the window and select View All.
    This will allow all of the TINA sim/analysis parameters to be displayed

    Scroll down to the parameter TR maximum time step. The default setting for this parameter is 10G.
    This allows TINA to adaptively adjust the transient time step during the simulation, and it doesn't place any useful limits on the max value of the time step.

    If the setting in your sim is 10G, please change it to a small value that allows your simulation to finish in a reasonable time.
    I used 1n, and the default sim ran quickly and seemed to fix the problem.

    Please try a sim and see if it fixes the problem.
    If it does, then the problem is that TINA was increasing the step size during the flat parts of the square wave, and wasn't reducing the step size quickly enough when it encountered a rising or falling edge. This was causing a tracking error at the edges.

    If it doesn't fix the problem, please let me know and we can look for a different root cause.

    Please let me know if you have any questions.

    Regards,
    John