Crystals VS Resonators

Thread Starter

Chug

Joined Aug 26, 2009
3
I have just purchased a ATmega168 development/programming board on ebay and in the description it mentioned that the kit may come with a 16 MHZ crystal or a 16MHZ resonator.

Is a crystal better or is a resonator just as good?

Bob
 

rjenkins

Joined Nov 6, 2005
1,013
A crystal generally has better frequency accuracy and stability, but 99% of the time the difference is too trivial to matter.

We use resonators in a lot of commercial products, specifically the three terminal type where possible as these have the capacitors built in, all you do is ground the center pin and connect the others to the CPU osc pins.

The only reasons we use crystals with microcontrollers is for specific frequencies where resonators are not available, or the very rare times it needs an accurate real-time clock (time of day) and this is not done by a separate RTC chip with it's own osc.
 

hgmjr

Joined Jan 28, 2005
9,029
Another side benefit, at least when an AVR is used, is that you can use the other pin normally associated with the connection of a crystal as an IO pin.

hgmjr
 

SgtWookie

Joined Jul 17, 2007
22,220
Unless you really need the accuracy of a crystal, you're much better off with the ceramic resonators. Crystals are relatively fragile, and are easily broken if dropped.
 

rjenkins

Joined Nov 6, 2005
1,013
You still need both oscillator pins to use a ceramic resonator!

You only need pin one if you use a self contained oscillator module, but that is a very different item.
 

hgmjr

Joined Jan 28, 2005
9,029
You still need both oscillator pins to use a ceramic resonator!

You only need pin one if you use a self contained oscillator module, but that is a very different item.
Thanks for that clarification. I neglected to make that distinction earlier.

hgmjr
 

nanovate

Joined May 7, 2007
666
Silicon oscillators are also pretty good from Maxim, Linear and ST. They are very accurate and stable plus are quite shock-vibe tolerant.
 

AlexR

Joined Jan 16, 2008
732
I have to ask, since I'm not sure, but is a resonator an LC tank circuit?
No its a ceramic piezoelectric device that acts very much like a quartz crystal. As others have said its not quite as accurate or stable as a crystal but its cheaper and less fragile than a crystal. It is also much more stable than a simple RC or LC circuit making it good enough for most microcontroller applications.
 
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