[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 15:09:33 -0800
Richard-
That might be true if there were physical differences between "series"
and "parallel" resonant crystals, but there aren't. From the Maxim app
note you referred to:
Resonance Mode
Crystals have two modes of resonance, parallel and series, and all
crystals exhibit both resonance modes. The oscillator circuit is
calibrated for one mode or the other, but not both. For applications
requiring no tighter than 100ppm frequency accuracy, resonance mode is
usually not an issue. If you are attempting to control frequency (or
time) to within 100ppm, however, the resonance-mode specification
becomes important. The crystal vendor's principal concern is in which
mode the crystal is calibrated during manufacturing. Knowing that
information, the crystal vendor then sets up an oscillator circuit with
the crystal in a customer-specified series resonance or parallel
resonance, and calibrates the crystal. Figure 2 shows crystal impedance
behavior versus frequency, and the relative location of each resonance
mode.
There are various "cut's" that are used in crystal manufacturing.
Depending on the angle of the cut with respect to the lattice structure
the vendor can set the inflection point of the tempco curve such that
crystal frequency change wrt to temp is relatively small (or not). There
are probably other factors that effect the temperature coefficient of a
quartz resonator, but the cut angle is a first order effect. As far as I
know the calibration frequency has little or no effect. (haven't seen
the Intel app note you referred to. Which one is it?)
-Ray
________________________________
From: Richard Jungert [mailto:r_jungert@xxxxxxxxxxx]
Sent: Monday, February 01, 2010 2:50 PM
To: Ray Anderson; steve weir; tlx6f@xxxxxxx; chundis@xxxxxxxxx; si list
freelist
Subject: RE: [SI-LIST] Re: follow up: Re: Query about Oscillator problem
Here is a great app note on how to specify a crystal.
http://www.maxim-ic.com/app-notes/index.mvp/id/726
According to Intel app note I just looked at the series resonant ones
are more sensitive to temp variation than parallel types.
Richard
> Subject: RE: [SI-LIST] Re: follow up: Re: Query about Oscillator
problem
> Date: Mon, 1 Feb 2010 14:19:47 -0800
> From: ray.anderson@xxxxxxxxxx
> To: r_jungert@xxxxxxxxxxx; weirsi@xxxxxxxxxx; tlx6f@xxxxxxx;
chundis@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> CC: raya@xxxxxxxxxx
>
> 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
> [mailto: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
> that
> > you may need to get a parallel resonant XTAL. Series resonant can
get
> you
> > 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
> here.
> >
> > 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
> Q.
> > > They are great for the crystal tuning caps where both
> characteristics
> > > 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
> PLL
> > > > 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
> the
> > PLL
> > > > start to lose locking. If the value is out of MCF5212 spec, the
> root
> > > > 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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