Hi,

Let me mention first of all that I haven't used spectre since school so please forgive dumb questions!

I'm trying to measure the jitter on a ring oscillator using spectre's pnoise analysis.

(1) When I try to select noisetype "pmjitter" and run pnoise analysis, I get the error:
Internal error found in spectre at freq = 200 MHz during PNoise analysis
       `pnoise'.  Please run `getSpectreFiles' or send the netlist, the
       spectre log file, the behavioral model files, and any other information
       that can help identify the problem to support@cadence.com.
   FATAL (CMI-2007): Error detected in file `dfiOut.c' at line 3037.
   FATAL (SPECTRE-21): Assertion failed.

In the first place, I had a tough time getting pss to converge, which wasn't the case when I selected noisetype "sources". The fundamental frequency is being calculated correctly. Parameters used:
sweeptype=relative
relative harmonic=1
threshold=0.75 (the swing of the vco is 0.5 to 1V)
crossing direction=rise
noisetype=pmjitter
maximum sideband=15
tolerance=1e-10

For pss,
tstab=100.6n
method=gear2only
steadyratio=0.1
I tried giving an initial condition as  well.

2) can I calculate the jitter from the phasenoise plot with noisetype=sources?

 I'm trying to use expression 16 and the spreadsheet from this appnote:
http://www.maxim-ic.com/app-notes/index.mvp/id/3359

But the jitter number seems very high and urealistic. What am I missing?

3) How do I calculate rms accumulated jitter from the phase noise plot?

Would deeply appreciate any insight into this! Thanks in advance!