Re: [ng-spice-devel] NEWS for the group


To ng-spice-devel@ieee.ing.uniroma1.it
From Lidia Daldoss <daldoss@ece.cmu.edu>
Date Fri, 07 Apr 2000 17:32:25 -0400
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Sender daldoss@ece.cmu.edu

Hi all,

1)about the LTE issue...

In the truncation error control provided by Spice3, the LTE associated
with the numerical integration of the energy storage devices is based on
a limit of acceptable error and used to control the timestep (del).
If we apply the trapeizodal rule, the allowable error for the step is:
tol= 1/12 x(3)(del*del)
x(3) 3rd derivative
Spice3 approximates  derivatives with divided differences and computes
the max timestep that could be chosen compatible with the error
constraints (tol).

In cktterr.c, we have:


 del = ckt->CKTtrtol * tol/MAX(ckt->CKTabstol,factor * FABS(diff[0]));
    if(ckt->CKTorder == 2) {
        del = sqrt(del);

ckt->CKTtrtol (=TRTOL,default value =7, as Nagel proposed) was
introduced because the truncation error estimation algorithm tends to be
too conservative.

2) someone can explain me why in Spice there is not charge conservation?
What is wrong in the model of the capacitor?
There are routines for  charge updating, associated with the energy
storage devices...

Thank you in advance,

Lidia

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