User Guide

Cautions and recommendations for simulation and analysis
191
Trading off computer resources for accuracy
There is a significant trade-off between accuracy and
computation time for parts modeled in the frequency
domain. The amount of computer time and memory scale
approximately inversely to RELTOL. Therefore, if you can
use RELTOL=.01 instead of the default .001, you will be
ahead. However, this will not adversely affect the impulse
response. You may also wish to vary TMAX and TSTOP,
since these also come into play.
Since the trade-off issues are fairly complex, it is advisable
to first simulate a small test circuit containing only the
frequency-domain device, and then after proper
validation, proceed to incorporate it in your larger design.
The PSpice defaults will be appropriate most of the time if
accuracy is your main concern, but it is still worth
checking.
Note
Do not set RELTOL to a value above 0.01. This can seriously
compromise the accuracy of your simulation.
Pspug.book Page 191 Wednesday, November 11, 1998 1:14 PM