Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice User Guide Convergence and "time step too small errors" October 2019 851 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. frequency the inductor dominates; above it the resistor does. This keeps the width of spikes from becoming unreasonably narrow. PSpice options TIME, the simulation time during transient analysis, is a double precision variable which gives it about 15 digits of accuracy. The dynamic range is set to be 15 digits minus the number of digits of accuracy required by RELTOL. For a default value of RELTOL = .001 (.1% or 3 digits) this gives 15-3 = 12 digits. This means that the minimum time step is the overall run time (TSTOP) divided by 1e12. The dynamic range is large but finite. It is possible to exceed this dynamic range in some circuits. Consider, for example, a timer circuit which charges up a 100uF capacitor to provide a delay of 100 seconds. At a certain threshold a comparator turns on a power MOSFET. The overall simulation time is 100 seconds. For default RELTOL this gives us a minimum time step of 100 picoseconds. If the comparator and other circuitry has portions that switch in a nanosecond then PSpice needs steps of less than 100 picoseconds to calculate the transition accurately. ■ Set RELTOL=.01 in the .OPTIONS statement. Example: .OPTIONS RELTOL=.01 This option is encouraged for most simulations, since the reduction of Reltol can increase the simulation speed by 10 to 50%. Only a minor loss in accuracy usually results. A useful recommendation is to set Reltol to .01 for initial simulations, and then reset it to its default value of .001 when you have the simulation running the way you like it and a more accurate answer is required. Setting Reltol to a value less than .001 is generally not required. ■ Reduce the accuracy of ABSTOL/VNTOL if current/voltage levels allow it. Example: .OPTION ABSTOL=1N VNTOL=1M Abstol and Vntol should be set to about 8 orders of magnitude below the level of the maximum voltage and current. The default