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Thread: RC oscillator
face BY : MCMANUS, Don email (remove spam text)


       I have an application which requires a an RC oscillator.  Since the
design will be subjected to high vibration in the field, it is felt that a
crystal or resonator would be too fragile.

       Right now we are operating at 4MHz, but this is may end up at 1 MHz
or below.

       The problem is that when we test the oscillator over temperature it
moves several percent between 25C and 50 C, at which point it can no longer
maintain serial communications because the clock has drifted too far. This
is unexpected because the we are using top quality high stability resistors
and capacitors, which should only move about 20-30 PPM/C each.

       I thought I had seen graphs of the stability of the RC mode from
device to device and over temperature, but I can't locate these in the
datasheet or app notes.

       I would like to know if anyone out there has experience with the RC
oscillators performance over extended temperature(we'd like to go up to
125C).  Hopefully I could get a few suggestions to stabilize our design.
Thanks in advance for any help

Don McManus
Bently Nevada Corporation


See also: www.piclist.com/techref/microchip/time.htm?key=oscillator
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