I am trying to run a Monte Carlo simulation of a 25GHz LC-VCO (vco followed by an ac-coupled buffer) for phase noise (mmsim-7.11, pss (harmonic balance) and pnoise). When I try a single run (no variability), the simulation finishes successfully without any errors or warnings. When I try running a Monte Carlo simulation (with process and mismatch), I am having one of the problems described below randomly (depending on the seed and starting run#). By the way, when I try to run a transient analysis in a Monte Carlo simulation with the same samples, the simulation finishes successfully. Could you please help?
1) After the first few samples, the simulator stops/freezes without any error messages in the output log.
2) At the first sample, I got the error message: "ERROR SPECTRE-16192: No convergence achieved with the minimum time step specified". I think this happens during the tstab. However the transient simulation does not have any convergence problems with the same set of samples.
Could you please help?
You didn't mention what subversion of MMSIM 7.1.1 you were using. If you are simulating with BSIMSOI devices, there is a known issue that is described in support.cadence.com Solution 11588618 which is fixed in the latest MMSIM 7.1.1 ISR available on downloads.cadence.com .
If the latest ISR doesn't resolve this issue, I recommend contacting Cadence Customer Support and filing a Service Request, attaching your spectre output logfile to the SR.
Customer Support Director - Analog/Mixed-Signal/RF AEs
Cadence Design Systems, Inc.
In reply to Tawna:
The latest ISR resolved the issue.
Thanks and regards,