Hi,
I wonder what would happen if you used a resonator with built in load caps?

Jeff Jolie
New England Automated
Machine Engineering, Inc.
jeff@neame.com

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Nicholas Uloth
> Sent: Friday, March 12, 1999 4:36 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Oscillating at low temperatures
>
>
> At 06:40 PM 3/11/99 +0000, you wrote:
> >Hi,
> >
> >On 12 Mar 99 at 0:15, Nicholas Uloth wrote:
> ><snip>
> >> Has anyone else been running pics at low temperatures - did
> you do anything
> >> special for the
> >> oscillator circuit ?
> >
> >I've just ran a sample of my boards (12C508 industrial temp range)
> >through the 50C to -10C temperature range, quickly.  They run fine.
> >I have run them before down to -25C with no detectable problems.
> >Some previous version of the same circuit ran outdoors in Antarctica
> >(-30C to -40C) and our customer thinks it worked fine....
>
> what voltage were you running at ?  The tricky thing is that it looks like
> the problem
> is due to temperature related changes inside the pic - because the problem
> also occurs when I only cool
> the uP and leave the oscillator circuit at room temp.
>
>
> >Are you using NPO capacitors on the crystal?
> yep
>
> >Do you use a series drive limit resistor?
> yes 100k
>
> >What does your crystal's datasheet say?
> Its rated to -40C, im using 10pF load caps instead of the
> recomended 12.5pF.
>
>
> Nic
>