RE : calculating the output power of a Quartz oscillator

Why would you use PSS and then use the time-domain waveform? Wouldn't it make more sense to use the frequency-domain output - that's complex after all?

Also, for a crystal oscillator, you might also want to consider using harmonic balance (unless the output is very square).

Regards,

Andrew

The two simulations (pss and hb ) give different (slightly) results.

Do the following setups make sense?

PSS input.scs

simulatorOptions options psfversion="1.4.0" reltol=1e-3 vabstol=1e-6 \

    iabstol=1e-12 temp=27 tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 \

    gmindc=1e-15 rforce=1 maxnotes=5 maxwarns=5 digits=5 cols=80 \

    pivrel=1e-3 sensfile="../psf/sens.output" checklimitdest=both  \

    sqldb_violating_ratio=yes

pss  (  vout  gnda  )  pss  flexbalance=yes  fund=10M  harms=100

+    errpreset=moderate  oscic=lin  oscmethod=onetier  tstabmethod=trap

+    annotate=status

Calculator function : ymax(leafValue( hb_spec_Pout "Design_Point" 1 )) gives 86uW

Harmonic Balance : input.scs

simulatorOptions options psfversion="1.4.0" reltol=1e-3 vabstol=1e-6 \

    iabstol=1e-12 temp=27 tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 \

    gmindc=1e-15 rforce=1 maxnotes=5 maxwarns=5 digits=5 cols=80 \

    pivrel=1e-3 sensfile="../psf/sens.output" checklimitdest=both  \

    sqldb_violating_ratio=yes

hb  (  vinv_xto_inv  vinv_xti_inv  )  hb  saveinit=yes  autoharms=yes

+   autotstab=yes  oversample=[1]  fundfreqs=[(10M)]  maxharms=[5]

+   errpreset=moderate  oscic=lin  oscmethod=onetier  annotate=status

Calculator function : ymax(pvi('pss "/vinv_xto_inv" 0 "/V_xosc/PLUS" 0)) gives 76.4uW

You mentioned that the output is pretty square, so I rather doubt that 5 harmonics would be enough - although you have "autoharms" set to yes, so I don't know how many it actually chose (the log file would show that). Understanding this is hard without seeing it, so I suggest you contact customer support - that's what it's for (submit a support case after logging in). Then maybe you can share the example, we can look at log files, and see what accuracy controls are affecting the difference (your expressions are different between the two and you have them the wrong way around, and the hb expression doesn't seem to actually include the output power expression).

Andrew

My comment was misleading. The output of the osc, the clock to the digital, is quite square but I case about power into the crystal. But the Quartz waveform is quite sinusoidal. The calculator functions are from the Main Results Viewer.

Results → Direct Form → Main form

Select pss (of hb), select power, select Terminal ( an ideal zero volt source) on input to crystal.

Is measuring the Power into a Quartz crystal by simulating the power into a terminal (of an ideal voltage source) a valid method in pss or hb?

Is measuring the Power into a Quartz crystal by simulating the power into a terminal (of an ideal voltage source) a valid method in pss or hb?