FAN5068 Component calculations and simulation tools

AN-6006

REV. 1.0.0 05/26/04

2

Figure 1. FAN5068.OPJ project

The parameters for this model are entered in the "Parameters" block on the lower left-hand corner of the schematic.

As such, there should be no need to edit the schematic itself.

Double click on any parameter in that block to set the values in the schematic. Once the schematic is set up, F11

(function key) will display the Bode plot.

To choose between Bode plot (AC small signal) and Transient response, go to the project window and right click the

appropriate model. If you are simulating for transient response, be sure to set up RLOAD. You will know if you

forgot this step, as the inductor current [I(L1)] trace will be much higher (probably beyond the Y axis limit) than the

pulse load current [I(I1)].

Alternately, from the schematic view, select the type of simulation profile from the drop-down box as shown below.

Figure 2. Simulation profile select drop-down

Troubleshooting the plot window

Some older versions of PSPICE may not automatically load the probe settings (which are contained in the *.prb

files). These settings define the XY axis settings, trace colors, and which signals are displayed. If you run a

simulation and the probe window has no trace, then add a trace, and input the expressions for the signals to plot:

Gain:

DB(V(Out)/V(Sig))

Phase:

P(V(Out)/V(Sig))

Copy and paste these expressions into the add trace window as shown below. The also schematic contains the

expressions for the BODE plot in the lower right hand corner