[SI-LIST] Re: follow up: Re: Query about Oscillator problem

  • From: Ray Anderson <ray.anderson@xxxxxxxxxx>
  • To: "Richard Jungert" <r_jungert@xxxxxxxxxxx>, "steve weir" <weirsi@xxxxxxxxxx>, <tlx6f@xxxxxxx>, <chundis@xxxxxxxxx>, "si list freelist" <si-list@xxxxxxxxxxxxx>
  • Date: Mon, 1 Feb 2010 14:19:47 -0800

The terminology of "series" or "parallel" resonance when speaking of
quartz crystal resonators refers to the resonance mode where calibration
was established. 

Physically there is no difference between a series and parallel resonant
crystal. The type of resonance utilized in the oscillator has to do with
the oscillator topology. Some oscillators require the crystal to exhibit
a low impedance at resonance (the series mode), whereas other oscillator
types require a high impedance (parallel mode) to sustain oscillation.

Using a "parallel" resonant crystal in a "series" resonant oscillator
will result in a slightly different frequency of oscillation than the
crystal vendor intended, but it shouldn't materially affect the
oscillator functionality.

-Ray Anderson
Xilinx Inc.

> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> On Behalf Of Richard Jungert
> Sent: Monday, February 01, 2010 1:49 PM
> To: steve weir; tlx6f@xxxxxxx; chundis@xxxxxxxxx; si list freelist
> Subject: [SI-LIST] Re: follow up: Re: Query about Oscillator problem
> Guys
> It may very well be that the series resonant quartz won't work and
> you may need to get a parallel resonant XTAL. Series resonant can get
> into trouble. I would go with the crystal type/mfg that Motorola
> recommends.
> I would bet dollars to doughnuts that the resonant type is the issue
> Richard Jungert
> > Date: Sun, 31 Jan 2010 15:20:46 -0800
> > From: weirsi@xxxxxxxxxx
> > To: tlx6f@xxxxxxx
> > CC: chundis@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: follow up: Re: Query about Oscillator problem
> >
> > Li, that is not correct.  NPO capacitors are high stability and high
> > They are great for the crystal tuning caps where both
> > are a plus.  But the high Q can actually create unwanted resonance
> > problems in the PLL power filter.
> >
> > Steve.
> > Li, Tianqi . (S&T-Student) wrote:
> > > Sree,
> > >
> > > I forget sth. You need to check the PLL filtering capacitors of
> MCF5212.
> > > In most cases CPU will leave out 2 or 3 power pins for filtering
> > > noise. Capacitors on these pins should also use NPO for a better
> > > performance.
> > >
> > > And you also need to find at what value of Vpp of XTAL droped to
> > > start to lose locking. If the value is out of MCF5212 spec, the
> > > cause is surely on XTAL tank circuit; If not, it might be XTAL's
> glitch
> > > aroused. You can use scope to test the eye diagram and find the
> glitch.
> > >
> > > Tianqi Li
> > >

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