supermoment wrote on Aug 7th, 2010, 4:04am:the diagram shows the conservative run overlapping with pss result.
I think you can understand you have to pay attention to accuracy of Transient Analysis of Cadence Spectre if you use it for VCO analysis.
Most serious issue is such irregular large deviation from correct value.
I often encounter irregular large deviation from correct value when I use Cadence Spectre.
You could not notice such large deviation, if you simulate only one point such as vc=0.8V.
Even if I use Golden Standard HSPICE, I can observe deviation from correct value if I don't tighten accuracy such as "delmax".
But I never encounter such extraordinal deviation when I use Golden Standard HSPICE.
Again see
http://www.designers-guide.org/Forum/YaBB.pl?num=1237627988/5#5I always set "maxstep" for VCO analysis if I use Cadence Spectre.