eldo_user

Speed and Accuracy
Integration Methods
From the user perspective, there are not many options. Clamping the maximum allowed time
step is usually the most radical solution, however this may slow down the whole simulation
significantly. Increasing the accuracy may also help.
If these oscillations occur, and they are a problem (for example because the testbench attempts
to measure currents with high accuracy), the solution is to switch to the GEAR method. Much
cleaner current waveforms will be produced by GEAR, however GEAR has its own undesirable
property to artificially damp natural oscillations of the circuit. Thus, for the analysis of pure
oscillators, or when trying to identify local or global instability problems in a design, GEAR is
not recommended, because it will tend to artificially stabilize any circuit. BE is even worse in
this respect.
If you want to gauge how these methods behave with respect to the damping of natural
oscillations, try the following: create a pure parallel LC network between a node you will
initialize at 1Volt (using a .IC statement) and the ground (0). Pick L and C and the transient
analysis duration, T, so that you can see about one hundred periods of the waveform
(T=100.sqrt(L.C).2.pi). Try it with TRAP, then with GEAR, and then with BE.
Related Topics
Time Step Control
Newton Iterations Accuracy Control
Global Tuning of the Accuracy—EPS
Global Tuning of the Accuracy—TUNING
Simulation of Large Circuits
Tips for Improving Simulation Performance
Eldo® User's Manual, 15.3 1247