Hello,
Spectre seems to set the maxstep for hb (during tstab) to be 1/100th the time period of Tone-1 by default, even if the maxstep specified is much larger. I couldn't find prior discussion/bugs on this behavior. Can anyone please let me know if this is expected?
In my example case, spectre seems to set maxstep to 3.85ps even when I ask it to set it to 100p. The period of tone-1 is 385ps and spectre seems to pick maxstep to be 1/100th that. I changed oversampling factor for curiosity - doesn't seem to make a difference.
I've attached input.scs and spectre.out for reference. Below are brief details from there. Please let me know if I'm missing something! Thanks a bunch for the help.
Raghu
Spectre Version: 18.1.0.235.isr3 64bit -- 8 Jan 2019 (APS enabled)
From input.scs:
hb hb tstab=1.05u saveinit=yes oversample=[2 1 1]+ fundfreqs=[(f_lo) (par_frf1) (par_frf2)] maxharms=[10 5 5]+ errpreset=moderate maxstep=100p tstabmethod=gear2only skipdc=yes+ annotate=status
parameters par_frf1=2.6G par_frf2=2.601G f_lo=2.595G
From spectre.out:
Important parameter values in tstab integration: start = 0 s outputstart = 0 s stop = 1.0501 us step = 1.0501 ns maxstep = 3.85356 ps ic = all useprevic = no skipdc = yes reltol = 10e-06 abstol(V) = 1 uV abstol(I) = 1 pA temp = 27 C tnom = 25 C tempeffects = all method = gear2only lteratio = 3.5 relref = sigglobal cmin = 0 F gmin = 1 pS rabsshort = 1 mOhm