On 6/15/07, Bob Blick <bbblick@sbcglobal.net> wrote:
> --- William Chops Westfield <westfw@mac.com> wrote:
> > What oscillator modes are you using?  Do resonators
> > need to
> > change mode with speed like crystals?  Do they need
> > to NOT
> > change modes?
>
> Of course I tried both XT and HS modes. But neither
> started reliably.

Even I know you know, one suggestion:
Keep the SMD area of the resonator very clean.
The OSCOUT route should have minimal parasitic capacitance
(add that to the 7pF of the PIC IO pin and to the resonator built in
capacitor value)
Measure and store the output level of the oscillation on your TEK
using a 10:1 proble and see the amplitude variation for all your
tested resonators.
The problem is the internal capacitors value and the Q factor of the system.
Check the OSCIN IO trigger level for your particular Vdd, and see the
lower limit of the amplitude oscillation (which is decreasing with
temperature increase).

The SMD resonators with good Q are packed in some white ceramics.
Heating the package above 250C for more than 1 minute will split the
package in two, so you may see how looks inside, maybe taking a look
under the microscope will be interesting. Also if you may cut from the
internal capacitor surface (the one connected on OSCOUT) you will see
interesting results.

Of course those operation are good only for understanding the problem
and maybe considering for the future that using 3 components is safer
than using one.

Vasile
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