FreeLists / si-list / [SI-LIST] Re: Crystal oscillator simulation in time domain by Pspice

["Chris Schmolze" <schmolze@xxxxxxxxxxx>]

Sogo,

Oscillators - use IOLEVEL=3D2 for slow ramp inputs to prevent getting
stuck in
'X' state

One of the problems in using a digital gate in an oscillator, is that
the default digital I/O level is set to 1, which means that the allowed
states are 0, R(rising), 1, F (falling), Z (high impedance) and X
(indeterminate).  Since an oscillator is trying to use a digital part in
the linear domain, it usually gets to R, F, or X and stays there as a
steady state, and never oscillates.

To fix this, go to the gate(s) you are using, and change their IOLEVEL
from 0(the default) to 2.  This goes to a simplified state machine that
basically has 0 and 1.  This should allow the oscillation to begin.

Regards,
Chris Schmolze


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Sogo Hsu
Sent: Wednesday, June 09, 2004 1:51 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Crystal oscillator simulation in time domain by
Pspice

Hi, Gurus,

I tried to simulate a typical oscillator and investigate the start-up=20
time by Pspice. The oscillator consists of an inverter and crystal.=20
the crystal was modeled by it's equivalent circuit. However, we were=20
unable to start up the oscillation successfully. It seems that is the=20
limitation of Newton-Raphson algorithm. The algorithm ensures the=20
circuit simulation can converge to solution. Accordingly, it gives up=20
the oscillation solution to avoid 'diverge' issue. How can I solve=20
this issue and bypass the converge requirement to achieve=20
oscillation? Thank you for your comments in advance.

Sogo Hsu Ph. D.
Foxconn

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