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Simulators >> Circuit Simulators >> Spectre convergence problem near END of a simulation
https://designers-guide.org/forum/YaBB.pl?num=1332546475

Message started by wave on Mar 23^rd, 2012, 4:47pm

Title: Spectre convergence problem near END of a simulation
Post by wave on Mar 23^rd, 2012, 4:47pm

Hello all - I'm using Spectre to run transients on a relaxation oscillator.
Using some normal oscillator tricks (Trapezoidal, InitCond), it starts to oscillate correctly.
Then near the END of the Trans simulation I get all sorts of warnings; the usual list of things blowing up, Rel tolerances, try this, try that.
ex: Failed test: | Value | > RelTol*Ref + Abstol

...update too large: ....

If I change the Trans sim time and/or accuracy (conserve/moderate/liberal) it does not change.
Trying Analog options now, but that's not helping much either.

This is steady state, so nothing SHOULD be changing drastically.
This is preventing me from running iterative corner sim loops.

Ideas?

thanks,
Wave

Title: Re: Spectre convergence problem near END of a simulation
Post by ywguo on Mar 29^th, 2012, 6:40pm

Hi wave,

There are many possible reasons. Probably the model is bad, any inductor inside your circuit, the simulator options ....

Please check the following.

Is there anything wrong in the circuit topology?
Does the oscillator operate steadily before it has the unconvergence problem?
Is there any step in supply?
Is there any inductor?
Do you set max time step? If NO, please set a reasonable value.
Switch to gear2only if the oscillator can start up with gear2only.

Best Regards,
Yawei