[SI-LIST] Re: crystal oscillator spice simulation
- From: Raj Raghuram <raj.raghuram@xxxxxxxxxxxxxxx>
- To: starsilic@xxxxxxxxx
- Date: Fri, 06 Oct 2006 13:25:44 -0700
You might also consider using software packages which find Periodic
Steady State, phase noise, jitter, etc.
Best Regards,
On Thu, 2006-10-05 at 22:59, Canes Venatici wrote:
> Hi all,
> I'm involved in characterizing crystal oscillator cell (available as
> netlist). I thought of putting the equivalent circuit of crystal and package
> parasitics and simulate it, for finding the frequency deviations in all
> process corners. I'd used some kick start for inductor by initializing it
> with some current. Does it represent the realtime situations. Or should we
> have to insert noise into the oscillator, which mimics actual scenario.
> Also I want to know whats the challenge involved in characterizing such
> scenarios. I mean, what we have to look in such characterizations. Why people
> say it takes much time to simulate, convergence issues etc. Are there any
> procedures for characterizing the crystal oscillator cells, which tells what
> and how to analyse.
>
> I just pasted my spice file. Please look into and tell where I may be making
> mistakes or what more analyses I should do to make it full fledged analysis.
>
>
> SPICE file for characterizing crystal osc.-----------
> *---------- OPTIONS AND PARAMETERS ---------------------
> .OPTIONS post list
> *.OPTIONS ACCURATE
> *.OPTIONS ABSTOL=1e-4
> *.OPTIONS RELTOL=1e-7
> *.OPTIONS DCON= 2
>
> .PARAM PVDD = 1.2
> .PARAM PIOVDD = 3.3
> .PARAM PVSS = 0.0v
> .PARAM PIOVSS = 0.0v
>
> *--------- POWER SOURCES --------------------------------------
> VVDD VDD 0 dc PVDD
> VVSS VSS 0 dc PVSS
> VVDDPST VDDPST33 0 dc PIOVDD
> VVSSPST VSSPST33 0 dc PIOVSS
>
>
>
>
> *---------- CIRCUIT DESCRIPTION ----------------------------------
> *-------------crystal------
> .subckt crystal12.5m x1 x2 kick=0
> r1 x1 a 12
> c1 a b 20f
> *l1 b x2 8.11m ic=kick $ 12.5MHz fundamenatal
> l1 b x2 8.11m
> c0 x1 x2 5p
> .ends crystal12.5m
> *---------------------------
>
> *------passive components for the osc
> *r0 CLKIN XTAL 1000K
> Cx1 CLKIN_OUT 0 10pf
> Cx2 XTAL_OUT 0 10pf
> Cstray1 CLKIN_OUT 0 6p
> Cstray2 XTAL_OUT 0 6p
>
> Cpin1 CLKIN_inter2 0 1.015pf
> Cpin2 XTAL_inter2 0 1.008pf
> Cpin3 CLKIN_OUT 0 1.015pf
> Cpin4 XTAL_OUT 0 1.008pf
>
> Lpin1 CLKIN CLKIN_inter1 7.35n
> Lpin2 XTAL XTAL_inter1 7.95n
> Lpin3 CLKIN_inter2 CLKIN_inter3 7.35n
> Lpin4 XTAL_inter2 XTAL_inter3 7.95n
>
> Rpin1 CLKIN_inter1 CLKIN_inter2 0.095
> Rpin2 XTAL_inter1 XTAL_inter2 0.0935
> Rpin3 CLKIN_inter3 CLKIN_OUT 0.095
> Rpin4 XTAL_inter3 XTAL_OUT 0.0935
>
>
> Xcrystal CLKIN_OUT XTAL_OUT crystal12.5m kick=2.5m
> Xpoc_xtalpad XTAL CLKIN XC PXD03DG
>
>
>
>
>
> *---------- ANALYSIS STATEMENT ---------------------------------------
> .tran 0.01n 0.3u
>
>
> .MEASURE TRAN tperiod TRIG V(XC) VAL=midvalue TD=.1u RISE=1
> + TARG V(XC) VAL=midvalue RISE=2
>
> .MEASURE TRAN twidth TRIG V(XC) VAL=midvalue TD=.1u RISE=1
> + TARG V(XC) VAL=midvalue FALL=1
>
> .MEASURE TRAN ttrans TRIG V(XC) VAL=lowvalue TD=.1u RISE=1
> + TARG V(XC) VAL=highvalue RISE=1
>
>
> .TEMP 25C
>
>
> .PARAM iovdd = 3.6v
> .PARAM vdd = 1.08v
> .PARAM lowvalue = 0.12
> .PARAM highvalue = 1.08
> .PARAM midvalue = 0.54
>
> r0 CLKIN XTAL 100K
>
> .end
>
> Regards
> Canes
>
>
>
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--
Raj Raghuram
Berkeley Design Automation (http://www.berkeley-da.com)
2902 Stender Way
Santa Clara, CA-95054-3213
Tel: 408.496.6600 x203
Cel: 408.390.7614
Fax: 408.496.6633
email: raj.raghuram@xxxxxxxxxxxxxxx
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