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UCC21520: Altium Simulation Error: Time Step Too Small

Yun Liu
Prodigy 115 points
Part Number: UCC21520

I was using PSpice for TI to run the simulation for this project, but I got this error where I have too many imported components. So I decided to edit the schematic on Altium instead.

After I started simulating on Altium by importing the file from OrCAD. I found out that my voltage source (on the left) is not giving any voltage, so I changed it to the VSRC (on the right), and was able to output correctly voltage in the operation point. (I added the Pspice simulation model to each of the imported components)

However, after that, I wasn't able to simulate the schematic anymore because it kept showing the error "Transient Analysis: Time Step Too Small". But my transient simulation parameter did not change.

So I started changing the parameter around. Changed the stop and step bigger (or smaller), and still not working. 

I also changed the "affect" file from document to project in the simulation dashboard, and it also doesn't work.  

I tried to simulate a regular circuit, a buck converter using the VSRC as my input voltage and PWM signal (VSRC can change to pulse wave) to see if I would get the same error. But I was able to simulate the schematic successfully with the correct simulation graph. 

 

So I am not sure how to fix the error. 

Here is my schematic for my project. 

 

(I modified this schematic with the VSRC source, and was unable to simulate it due to the error)

 (Have not yet modified the voltage source yet, but was able to simulate the transient graph without the error.)

  • 0
    TI__Expert 4065 points

    Hello,

    I will review this information and see what can be done by Thursday or sooner.

    Regards,

    Krystian

  • 0 in reply to Krystian Plaskota
    Prodigy 115 points

    Hello Krystian, 

    Thank you! I also found out that if I disable the PWM signal source (the pulse signal), it will be able to simulate without the error with the circuit being opened. I thought it might be an imported OrCAD file problem, so I switched the signal source to VSRC, which still not working.

    Yun

  • 0 in reply to Yun Liu
    TI__Expert 4065 points

    Hi Yun,

    Are you getting any additional details from the session log or command window after the error? Also we have two pspice models for the UCC21520 on the product page, have you tested that this error appears on both? I believe one of them will have no restrictions on how many sources you can measure in your schematic which I think would solve your first issue before the timestep one. 

  • 0 in reply to Krystian Plaskota
    Prodigy 115 points

    Hi Krystian, 

    Here is the additional detail from the output window.

    I used either the Unencrypted Pspice Transient Model or the regular Pspice transient model from the TI UCC21520 site. I will try both and see if I still get the same message. Thank you for the suggestion. 

    Yun Liu

  • 0 in reply to Krystian Plaskota
    Prodigy 115 points

    Hi Krystian, 

    There was only 1 simulation file that I can use for Pspice for TI on the product page. The unencrypted Pspice transient model is for Altium, which is the one I used on Altium. And the rest of the simulation files aren't for either Pspice for TI or Altium. But I figured out the problem for Pspice for TI simulation. The error that I posted was more like a warning. After I place a probe/marker, I was able to simulate correctly. Though, I would still want to resolve the problem about the time step too small on Altium. 

    Yun Liu

  • 0 in reply to Yun Liu
    TI__Expert 4065 points

    Hi Yun Liu,

    Both models are for PSpice and we only support the PSpice and Tina simulation platforms. Unfortunately I can't assist with debugging the errors on Altium since using Altium for simulation isn't my area of experience. I would check to see if there is incompatibility with the sources you used and the model in some way, maybe the sources that were originally placed there had certain parameters or function that the VSRC didn't have that caused this type of error to occur. Sorry I can't help of more than that.  

    Regards,

    Krystian

  • 0 in reply to Krystian Plaskota
    Prodigy 115 points

    Hi Krystian, 

    Thank you for getting back to me and helping me. I will try to figure it out myself then. 

    Yun Liu