Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice User Guide Convergence and "time step too small errors" October 2019 852 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. values are Abstol=1pA and Vntol=1uV. These values are generally associated with IC designs. ■ Increase ITL4, but to no more than 100, in the .OPTIONS statement. Example: .OPTIONS ITL4=40 This increases the number of transient iterations that PSpice will attempt at each time point before it gives up. This is particularly effective at solving convergence problems when the simulation needs to cover a long time period, and fast transitions occur within the circuit during that time. Values greater than 100 won't usually bring convergence; unnecessarily large values can cause. ■ Skipping the bias point The SKIPBP option for the transient analysis skips the bias point calculation. In this case the transient analysis has no known solution to start from and, therefore, is not assured of converging at the first time point. Because of this, its use is not recommended. Its inclusion in PSpice is to maintain compatibility with UC Berkeley SPICE. SKIPBP has the same meaning as UIC in Berkeley SPICE. UIC is not needed in order to specify initial conditions. It should be used as a last resort if there is trouble getting the transient analysis to start because the DC operating point can't be calculated. The initial guess for dc could be made from results of such transient analysis; and then transient analysis could be re-run with operating point. You should add any applicable .IC and IC= initial conditions statements to assist in the initial stages of the transient analysis. Be careful when you set initial conditions, for a poor setting may cause convergence difficulties. ■ Increasing the ABSTOL and CHGTOL While modeling a mechanical system with an RC circuit, where capacitors are in the order of Farad and current impulses is around 10x A, increase CHGTOL and ABSTOL by six order of magnitude. For example, change CHGTOL from 0.01e-012 to0.01e-006. Simulate the circuit and then start tightening the ABSTOL and CHGTOL values until a convergence error is