OK, so it is the Load Cap value I'm looking at then (with the consideration
that's for two caps in series, plus parasitics)?

On 1/8/06, David VanHorn <dvanhorn@microbrix.com> wrote:
>
> >
> > The part specifies B2 capacitance for the 50Mhz crystal, and a B2F for
> the
> > 25Mhz I need.  Both are from the same company and have the same data
> > sheet.
> > Any help?  What is the B for?  Does the two mean I need twice the cap.
> of
> > the crystals value?
>
>
>
> The part number mouser calls out dosen't match the system used in the
> ordering options in the data sheet.
> You can always call them and ask..
> I'd expect to see a part number like: AB-50.000-18-R15-B-2-X-F
> There's a note at the bottom that says "left blank if standard",  but I
> don't see how they show you what's "standard" here.
> I'd call abracon in the morning and ask.
>
> Now.. The load capacitance number is not the value of the caps to use.
> The two caps are in series from the crystal's point of view.
> Basically, double that, and subtract 5 pF (as a first guess) for parasitic
> capacitance in the circuit.
> That gives you 31pF and the closest value without going over would be
> 27pF.
> Try that, check operating frequency and oscillation margin, and then
> adjust
> if you need to.
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--


Shawn Wilton (b9 Systems)
http://black9.com
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