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Simulators >> Circuit Simulators >> How to set maximum and minimum allowed voltage for hspice convergence?
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Message started by neoflash on Mar 20^th, 2014, 11:32am

Title: How to set maximum and minimum allowed voltage for hspice convergence?
Post by neoflash on Mar 20^th, 2014, 11:32am

One of my simulation tends to converge to several thousands volts or negative voltage before totally give up.

If there is a knob to set the max and min allowed value during initial condition convergence, that may help simulator to converge.

Is there such knob available in hspice?

Title: Re: How to set maximum and minimum allowed voltage for hspice convergence?
Post by Geoffrey_Coram on Mar 24^th, 2014, 12:31pm

I have a vague recollection of a way to set a maximum per-iteration change of voltages. However, I don't think this is necessarily a good idea. The linear solver can end up with some crazy values when trying to use Newton's method to solve a nonlinear circuit. Generally, the simulator vendors have some sophisticated methods of improving convergence, and any attempts to tinker with the voltages might end up working against the internal tricks.

Title: Re: How to set maximum and minimum allowed voltage for hspice convergence?
Post by Andrew Beckett on Apr 7^th, 2014, 10:56am

I have also seen this kind of behaviour caused by poor Verilog A models. For example, I have seen a few cases where people model non-linear resistance with a quadratic (or higher order) equation, neglecting the fact that quadratic equations have multiple roots. If those roots represent completely non-physical behaviour, the simulator doesn't know that - so it may be a "correct" solution to have large negative voltages if the model is not reasonable...

Regards,

Andrew.