Solution
Simulation errors can arise for different reasons. To resolve these issues, first let the
Convergence Assistant attempt to solve the problem. If it is not able to fix it, look for the following causes:
- Floating components (i.e. parts with unconnected pins); these can go into the SPICE matrix, even if they are not being used, but can cause difficulties later.
- Extremely tiny resistor values; these enter the SPICE matrix as 1/resistance, creating large calculations. Some native components, like the SPST switch, have low resistance values. Try the following modifications in the circuit:
- Use the GROUND component to add a clear reference to the circuit.
- Increase the minimum resistance of the component.
- Use a different component that provides the same functionality.
- Direct voltage source across P-N junctions; this usually happens with LEDs and indicator components.
- Parallel voltage sources and inductors.
If you are still getting convergence issues after checking for the above, your next step is to adjust tolerances. You can change the tolerances by doing the following:
- Select Simulate»Interactive simulation settings.
- Select the Analysis options tab.
- Click Customize ...
- Under the Global tab you can adjust the tolerances, using the following guidelines:
- Increase RELTOL to no greater than 0.01.
- Increase VNTOL to no greater than 1e-3.
- Increase ABSTOL to no greater than 1e-6.
- Under the Transient tab, change the Integration method [METHOD] to Gear.