AVR-Chat

Hi Dave,
 
All crystal oscillators are "amplifiers" to some extent I don't think you
would see any huge current draws from adding the capacitor although I
understand your point.
 
And yes the chip was an ATm323 running at 8MHz as far as I remember.
 
Best regards
Lasse
 
  _____  

From: Dave VanHorn [mailto:dvanhorn@dvanhorn.org] 
Sent: 4. januar 2005 18:08
To: AVR-Chat@yahoogroups.com; AVR-Chat@yahoogroups.com
Subject: RE: [AVR-Chat] multiprocessing with AVR (2)
 
At 12:01 PM 1/4/2005, Lasse Madsen wrote:

>Hi Dave,
>
> >That would be bad. There's nothing to balance in this case, you're just
> >using the xtal sections as amplifiers.
>
>I disagree, depending on the internal design of the oscillator not using a 
>capacitor could cause it to stop oscillate (I have tried it without just 
>now and it works but I would still recommend it)

It's just an amplifier.  If you feel you must load it, then load it with a 
resistor, something that won't make it draw huge current spikes on the 
transitions.

>
> >>On the MASTER a 1Mohm between XTAL1/2 and a series resistor from XTAL2 
> to crystal of a hundred ohms is a good idea.
>
> >Why?
>
>The 1Mohm parallel resistor gives a nicer oscillation (check your scope) 
>and the 100R resistor reduces harmonics.

Hmm. I would be very reluctant to alter the osc circuit without knowing 
exactly what I was affecting in the chip.



>
>If you have a spectrum analyzer available try first without the 1Mohm then 
>try adding it would maybe see that this also reduces harmonics from the 
>crystal a little but the 100R resistor does the job much better. I got 
>this information attending an EMC coarse because one of our PCB's failed 
>to comply with EMC standards adding the 1M and 100R resistor did the job.

Was this an AVR? 



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