Hi,
I am working on an oscillator.
I am trying to shorten my corner PSS simulations (shooting method).
I am working with spectre, mmsim13.1.0
Convergence seems tricky on that circuit, so I tried (more or less) successfully what was proposed e.g. in
http://community.cadence.com/cadence_technology_forums/f/33/t/28744 and other places:
* do a long "liberal" tstab simulation,
* write the result with "writepss" (from PSS options)
* change convergence options to conservative & tighten lteratio, eliminate tstab but read the final result from the previously specified file with "readpss"
* rerun sim & enjoy
* I subsequently start also a phase noise simulation.
--> the simulation appears to converge immediately after loading that file.
Now, if I change process corners and temperature
(a) I have the same immediate apparent convergence at 1st shot
(b) the amplitude of oscillation does not change at all, which is an indication of fault; in previous simulation I always saw PVT variance, of course)
(c) phase noise simulations DO vary over PVT, but the results are a bit strange - did I invent a circuit that gets less noisy at higher temperature? ;)
Obviously I'm not really getting trustworthy results.
==> QUESTION:
? can I reuse tstab results from nominal process corner @ T=300K and expect that in subsequent PVT sims the deviation from this starting point will be recalculated to satisfy corner/temperature conditions?
? if I can expect that: which parameters do I have to set to force the simulator to do so?
many thanks in advance for your comments!
Martin