eldo_user

Setting Up An Analysis
DC Convergence Troubleshooting
• .IC in the Eldo Reference Manual
• .NODESET in the Eldo Reference Manual
• .RAMP in the Eldo Reference Manual
• .RAMP_SUPPLY in the Eldo Reference Manual
• Options GRAMP, PSTRAN, DPTRAN, and NOCONVASSIST in the Eldo Reference
Manual
• Options VMIN and VMAX in the Eldo Reference Manual
Related Topics
DC Convergence Troubleshooting
DC Convergence Troubleshooting
This topic describes some basic steps you can perform to help troubleshoot common DC
operating point (DCOP) convergence problems in Eldo.
Causes
Most convergence problems are related to one of the following:
• Devices and device models.
• Circuit topology (open loop, closed loop, hierarchical).
• Simulator setup (usually through simulation commands and options).
In DC analysis, the main causes of convergence failure are:
Solution
• Model discontinuities.
• Absence of (or insufficient) initial conditions.
• Instability in the circuit, bistable circuit blocks, and so on.
• Unpractical impedance levels (also check the units are correct: m is milli).
To improve DC convergence, do at least one of the following:
• Check circuit connections, especially for nodes with two connections or floating nets.
• Use initial conditions for important nodes:
.IC V(node)=...
• Increase ITL1 to 200, 300, or even 400; this increases the number of allowed DC
iterations before the simulator gives up:
Eldo® User's Manual, 15.3 213