User Guide

Phase Three: Runnin
g
an Optimization 2
-15
The constraint type specifies the required relation between
what is evaluated (as defined in the Evaluate text box) and
the target value (defined in the Target text box).
To define the constraint for power dissipation in
R1
The power dissipated in R1 must be less than or equal to
4 mW±400 uW. Define the constraint by doing the following:
1
In PSpice Optimizer, from the Edit menu, select
Specifications.
2
In the Specifications dialog box, click Add.
3
Enter the power (Pc) constraint properties as shown in the
following Edit Specification dialog box.
The Evaluate text box contains the expression for measuring
dissipated power. For each iteration, Probe will compute
dissipated power by taking the product of the voltage across
the resistance and the current through it.
4
To calculate the performance of the design for initial
parameter and specification values only (one iteration):
a
From the Edit menu, select Reset Values.
b
From the Tune menu, select Update Performance.
Note the appearance of the progress indicator in the Pc
box. Since Pc is a less than or equal to constraint, the
The constraint specification
settin
g
s are:
Name = Pc
Tar
g
et = 4mW
Ran
g
e = 400uW
Constraintselected
Type = <=tar
g
et
Analysis= DC
Circuit File= mydiode
Evaluate= i(r1)*v(r1:1,r1:2)
pro
g
ress indicator
See Progress indicator on
page 3-7 for more on the
different kinds of pro
g
ress
indicators and how to interpret
them.