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On Mon, Feb 24, 2025 at 09:03 AM, john23 wrote:

Hello ,I have the following file which is presenting an error shown below

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Convergence Failure: ?Time step too small; time = 8.11724e-08, timestep = 1.25e-19: trouble with instance "u1:DSC1"

I assume this is the failure you asked about.

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"Time step too small" errors are unfortunately difficult to deal with.? If this is your first time encountering a "timestep too small" error, "welcome to the club".

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"Time step too small" errors happen for this reason.? When SPICE can't converge at any timepoint, it backs up to the previous one, sets the time step smaller (I think by a factor of 8), and tries again.? It is more likely to find convergence by not trying to go too far into the future, so a smaller timestep after the last good point is more likely to solve, and then it can move on.

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But occasionally that doesn't work.? It keeps trying smaller and smaller timesteps, until eventually the timestep gets ridiculously small, and SPICE/LTspice aborts with that error message.

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The root problem is most likely because there is something in the circuit that behaves badly.? Maybe a component's function or its derivative has a discontinuity.? Both are bad for SPICE and should never happen, but many models have discontinuities and can lead to these problems.? The best remedy is to fix the models.? But often we can't do that.? There are a handful of other things that can sometimes help,?

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Download the FAQ file.? Open it and read until you find the section about "time step too small" errors, and start reading.? There are a couple dozen suggestions that MIGHT help.? There is no guarantee that you can ever fix a "time step too small" error.

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When I ran your simulation, I do not (yet) have a "time step too small" error, but it has not found the initial DC solution yet.? Time step too small errors can happen even during the initial DC solution phase, because one of the algorithms is "Pseudo-Tran", which applies the transient solver to finding the DC solution.? Sometimes it can abort in that phase, even though it is not a .TRAN simulation at all.

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Andy

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Hello ,I have the following file which is presenting an error shown below

When I added the following spice command it ran no problem.

Is there a manual an intuition regarding why this spice command solved the problem?

Ltspice file is attached.

Thanks.

spice command solution

.options cshunt =10f gshunt=10n abstol=10n vntol=1m

/g/LTspice/files/Temp/PID_section_united_AC_separate.zip

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error: