Thank's Joe,
btw, my aunts are not drinking (toooo) much :)


top 10 wishes,
Vasile


On Thu, 28 Aug 2003, Jinx wrote:

> >   OK, I will re-formulate a little my question. The external RC
> > oscillator works based on the RC time constant. However
> > because of the leackage curents can't be used any value for
> > R. Assuming the parasitic input pin capacitance is between
> > 10...15pF, then it's posssible to use just a resistor for the RC
> > oscillator. Now the question:
>
> > 1.which is the resistor range for a safe and stabile oscillator
> > operation?
>
> The recommendation is 3k < R < 100k and C > 20pF. This is
> in the F877 and 12C671 datasheets for example. And also from
> the 12C671 datasheet -
>
>  "Although the oscillator will operate with no external capacitor,
> we recommend using values above 20pF for noise and stability
> reasons. With no or small external capacitance, the oscillation
> frequency can vary dramatically due to changes in external
> capacitances, such as PCB trace or package lead frame". And
> presumably humidity too. "The variation is larger for larger R....."
> etc etc
>
> Similar advice in the F877 d/s
>
> So you can get by with no external capacitor but expect the
> frequency to wobble around like a drunk aunt at a Christmas party
>
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