Re: [LTSPICE] crystal circuit modeling settling time and certainty

On Tue, 28 Jun 2005 15:18:37 GMT, "colin"
<no.spam.for.me@xxxxxxxxxxxx> wrote:

>"Helmut Sennewald" <helmutsennewald@xxxxxxxxxxx> wrote in message
>news:d972c9$b3g$00$1@xxxxxxxxxxxxxxxxxxxx
>> I have summarized my ideas about crystal circuit simulation
>> from previous postings to user groups. Maybe not all are
>> necessary or helpful in your case.
><snip>
>> 4.
>> Try to precharge the important nodes with ".ic" to
>> reduce startup settling time.
>
>Hi as you sugest im trying to set up initial conditions with .ic for my
>crystal, I want to specify the current but as i can only do this for an
>inductor how do i reference the equivalent inductor inside the crystal
>circuit or any other component for that matter inside a subckt (within a
>subckt)? i cant seem to find this in the help file.
>
>I know this is actualy an ordinary capacitor (and i have set it inside a
>subckt to calculate the corect component values from the freq/q etc) so does
>this mean it is inacesible ?
>
>I gues i can either add an inductor in series with it or expand the
>capacitor parasitics into the subckt, or try to make it zero current at t=0
>but this would complicate things a bit. (especialy as i have 2 crystals)
>
>Colin =^.^=
>

Trying to ".IC" within the crystal will probably be difficult. If I'm
not trying to prove startup, I simply put an atrocious skewing .IC
within the oscillator itself, or use a "kick-start" current pulse.

On the other hand, if you're simply .AC simulating a crystal filter,
you just need to force very small frequency steps... like Fo/Q/100, if
you want to really have a handle on the transitions.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
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| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
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