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

 

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.

 

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

 

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

Just for information, this is true for PICs too.

 

Just for information, this is true for PICs too.

I suspected at much but my experience base is confined to AVR.

hgmjr

 

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.

 

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.

 

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

 

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

 

I have to ask, since I'm not sure, but is a resonator an LC tank circuit?

 

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.