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arsenal
Joined: 22 Sep 2005
Posts: 20
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 Posted:
Thu Nov 17, 2005 10:57 pm Post subject:
how to set up in spectre to make crystal oscillator start up |
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i have setup a crystal oscillator using inverter
and the netlist is shown as below:
m0 xo xi vdd vdd pch_33 l=0.5u w=2u m=1
m1 xo xi 0 0 nch_33 l=0.5u w=1u m=1
c1 xi 0 16p
c2 xo 0 16p
rf xo xi 1meg
v0 vdd 0 pwl 0 0 100u 3
xi0 xi xi xtal
.subckt xtal n1 n2
rs n1 n5 55k
ls n5 n7 11.233e3 ic=1e-7
cs n2 n7 2.1f
c2 n2 n1 1.1p
.ends xtal
and i have simulated the open loop gain and it's about 16dB, and the gm at steady state is about 500uS(<gmmax and >gmcrit), however, after powerup, the oscillator will enter the steady state(xo and xi remains at about 1.45) and never oscillate. （ and i have used option accurate and method=gear, and transient step is 1ns)
So anyone help me!!Thanks a lot
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okguy
Guest
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| Posted:
Fri Nov 18, 2005 9:10 am Post subject:
Re: how to set up in spectre to make crystal oscillator star |
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Did you check your phase margin so that it can oscillate?
How long is your simulation? It usually takes ms to start... to speed it
up, you can set an initial current in the crystal inductor. |
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arsenal
Joined: 22 Sep 2005
Posts: 20
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| Posted:
Thu Nov 24, 2005 1:55 am Post subject:
re:how to set up in spectre to make crystal oscillator start |
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sure, i have checked the gain which is higher than critical gain and less than the max gain and is enough for oscilation to startup,
and i have set initial current of the inductor,anyway, the oscillation will stop after some time.
so what shall i do? how can i setup the hspice options for oscillation to startup?
thanks
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