Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice User Guide Monte Carlo and sensitivity (worst-case) analyses October 2019 599 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. For example, during the sensitivity analysis, the parameter is varied once affecting all devices referring to it and its effect on the collating function is recorded. For the worst-case analysis, the parameter is changed for all devices by LOT + DEV in the determined direction. See the example schematic in Figure 13-17 and circuit file in Figure 13-18. Figure 13-18 Circuit file using VARY BOTH. In this case, V(3) is maximized if: ■ Rwc1 and Rwc2 are both increased by 10% per the LOT tolerance specification, and ■ Rwc1 is decreased by 5% and Rwc2 is increased by 5% per the DEV tolerance specification. The final values for Rwc1 and Rwc2 should be 105 and 115, respectively. However, because Rwc1 and Rwc2 are varied together during the sensitivity analysis, it is assumed that both must be increased to their maximum for a maximum V(3). Therefore, both are increased by 15%. The purpose of the technique is to reduce the number of simulations. For a more accurate worst-case analysis, you should first perform a worst-case analysis with VARY LOT, manually adjust the nominal model parameter values according to the results, then perform another analysis with VARY DEV specified. Gaussian distributions Parameters using Gaussian distributions are changed by 1σ (one sigma) for the worst-case analysis. Note: The default Gaussian distribution shall have the sigma value of 3. WCASE VARY BOTH Test Vin 1 0 10V Rs 1 2 1K Rwc1 2 3 Rmod 100 Rwc2 3 0 Rmod 100 .MODEL Rmod RES(R=1 LOT 10% DEV 5%) .DC Vin LIST 10 .WC DC V(3) MAX VARY BOTH LIST OUTPUT ALL .ENDS