ceramic oscillators

[Jamie Morken]

Hi all,

Is it ok to substitute a crystal with a ceramic resonator for driving a
microcontroller such as the AVR atmega8?
I would like to try using a supersmall ceramic oscillator instead of the
larger package HC49 crystals, and am wondering about the differences between
the two. From reading the specs I can see that the ceramic resonators are
typically far less accurate but are there any other drawbacks besides this?

The Murata "ceralock" ceramic resonators from digikey look pretty good. Any
other links to good small surface mount ceramic resonators at 16MHz?

cheers,
Jamie Morken

 

[Leon Heller]

Hi all,

Is it ok to substitute a crystal with a ceramic resonator for driving a
microcontroller such as the AVR atmega8?
I would like to try using a supersmall ceramic oscillator instead of the
larger package HC49 crystals, and am wondering about the differences between
the two. From reading the specs I can see that the ceramic resonators are
typically far less accurate but are there any other drawbacks besides this?

The Murata "ceralock" ceramic resonators from digikey look pretty good. Any
other links to good small surface mount ceramic resonators at 16MHz?

I often use ceramic resonators with AVRs, PICs etc. Apart from accuracy
and stability they don't have have any disadvantages. Another advantage
is that they can be obtained with capacitors built-in.

Leon

 

[Paul Burridge]

I often use ceramic resonators with AVRs, PICs etc. Apart from accuracy
and stability they don't have have any disadvantages. Another advantage
is that they can be obtained with capacitors built-in.

Yes, the three-pin type. What's the advantage of these? |'d imagine
they'd make trimming the resonator much more difficult...

 

[Spehro Pefhany]

Yes, the three-pin type. What's the advantage of these? |'d imagine
they'd make trimming the resonator much more difficult...

66% saving in number of parts. One less part number on the BOM.It is
rare to fool with the frequency of a resonator, they are used in
situations where the +/-0.5% or whatever tolerance is more than good
enough.

Best regards,
Spehro Pefhany

 

[Rene Tschaggelar]

Hi all,

Is it ok to substitute a crystal with a ceramic resonator for driving a
microcontroller such as the AVR atmega8?
I would like to try using a supersmall ceramic oscillator instead of the
larger package HC49 crystals, and am wondering about the differences between
the two. From reading the specs I can see that the ceramic resonators are
typically far less accurate but are there any other drawbacks besides this?

HC49 cristal packages are outdated. There are smaller ones, such as
SMU4

Rene

 

[James Meyer]

Yes, the three-pin type. What's the advantage of these? |'d imagine
they'd make trimming the resonator much more difficult...

Practicaly nobody trims ceramic resonators except hobby designers. You
typically use ceramic resonators when you want a cheap, fairly accurate
frequency source that you *don't* have to muck about with. If you feel that
ceramics need trimming then you're using the wrong part, it should be a quartz
crystal.

Jim

 

[Ken Smith]

HC49 cristal packages are outdated. There are smaller ones, such as
SMU4

Unless you are looking for a low noise crystal. Low noise crystals are
still in the larger packages.

 

[Wouter van Ooijen]

Is it ok to substitute a crystal with a ceramic resonator for driving a

microcontroller such as the AVR atmega8?

I am no AVR specialist, but if the datasheet says it is possible it
will be OK.

I would like to try using a supersmall ceramic oscillator instead of the
larger package HC49 crystals, and am wondering about the differences between

HC49S is much smaller, even smaller than the ceramics I know, but of
course the two capacitors spoil this.

the two. From reading the specs I can see that the ceramic resonators are
typically far less accurate but are there any other drawbacks besides this?

positive: more shock-resistant than crystals, and often cheaper.
Build-in capacitors mean less board space, less components to place.

negative: less accurate, but enough for asynch serial communication.


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
PICmicro chips, programmers, consulting

 

[gwhite]

Hi all,

Is it ok to substitute a crystal with a ceramic resonator for driving a
microcontroller such as the AVR atmega8?
I would like to try using a supersmall ceramic oscillator instead of the
larger package HC49 crystals, and am wondering about the differences between
the two. From reading the specs I can see that the ceramic resonators are
typically far less accurate but are there any other drawbacks besides this?

The Murata "ceralock" ceramic resonators from digikey look pretty good. Any
other links to good small surface mount ceramic resonators at 16MHz?

A ceramic oscillator will start up faster than a "similar" crystal oscillator.
For power saving sleep/wake-up projects, start time can sometimes be more
important than absolute accuracy.