LTSPICE: equally spaced timesteps

I cannot find the similar spice directive like ".option interp"(in HSPICE) or "strobeperiod"(in Spectre) in LTSPICE.
In LTPISCE, I do the FFT twice, but lose accuracy during the transient edge.

Is there anyway to set equal timestep in transient simulation?


  • +1
    •  Analog Employees 
    •  Super User 
    on Apr 13, 2021 5:59 AM

    Hi you can set the maximum timestep iin the simulation command setup window. This ensures that there are everywhere sufficient points. 

    the other thing is to simulate for long enough time and select a fitting number of points for the simulated time. Switch of the Smoothing and select a proper Windowing.

    use the altermnate solver.

    Disable compression (as a directive in the circuit place a spice command 

    .options plotwinsize=0)


    This are the things which come to my mind on the first view.

  • At the beginning, it was to solve the problem that the simulation time of the large matrix was too long in LTSPICE.
    I tried to modify the circuit from the original two path to one path+switch, and expected to use the delay process so that the result1 and result2 can perform point-to-point operations.
    However, during the delay process, the waveform is distorted by the unequally time step.
    At this stage, only the Maximum Timestep can be reduced to reduce the distortion, but it will be accompanied by the problem of increasing the simulation time.
    Thank you for providing these methods. If there are any tips Paintings that can reduce the simulation time are also welcome to share.

  • +1
    •  Analog Employees 
    •  Super User 
    on Apr 16, 2021 8:28 AM in reply to terrel

    You could use the .save command to save only the interesting nodes. This reduces the saved data.

    You can try to operate the simulation in a ramdisk. This could speed data saving and access. 

    Don't plot during the simulation can help as well.

    Relaxing accuracy can help as well, but I undersatnd that you are really looking at the details. (For circuit simulation this could be appropriate)

    Sometimes limiting the number of threads helps. Since there is some communication and wait time between the threads.

  • +1
    •  Analog Employees 
    on Apr 16, 2021 1:41 PM in reply to Willy67

    These are all good tips. 

    I will also add something I've learned recently - pause any syncing apps (OneDrive, DropBox, etc) while running sims.


  • Thank you for providing several accelerated method.

    If I have a breakthrough someday, I will feedback it with you.