User Guide

Default Options 4
-15
To control parameter perturbation when
calculatin
g
derivatives
1
Enter a value in the Delta text box that defines a fraction of
the parameter’s total range.
Example: If a parameter has a current value of 10
–8
, and
Delta is set to 1% (the default), then the PSpice Optimizer
perturbs the parameter by 10
–10
.
The 1% default value is suitable for the accuracy of typical
simulations.
2
If the accuracy of your simulation is very different from
typical (perhaps because of the use of a non-default value
for either RELTOL or the time step ceiling for a Transient
analysis), then change the value of Delta as follows:
• If simulation accuracy is better, decrease Delta by an
appropriate amount.
• If simulation accuracy is worse, increase Delta by an
appropriate amount.
Note
The optimum value of Delta varies as the square
root of the relative accuracy of the simulation. For
example, if your simulation is 100 times more
accurate than typical, you should reduce Delta by
a factor of 10.
Limitin
g
Simulation Iterations
(Max. Iterations Option)
The Max. Iterations option defines how many attempts, at most,
the PSpice Optimizer can make before giving up on the solution,
even if the optimizer is making progress.
To limit the simulation iterations
1
In the Max. Iterations text box, enter an integer value that
defines the maximum number of attempts you will allow the
PSpice Optimizer to make.