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ceramic oscillators

Discussion in 'Electronic Design' started by Jamie Morken, Feb 26, 2004.

  1. Jamie Morken

    Jamie Morken Guest

    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
     
  2. Leon Heller

    Leon Heller Guest

    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
     
  3. Yes, the three-pin type. What's the advantage of these? |'d imagine
    they'd make trimming the resonator much more difficult...
     
  4. 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
     
  5. HC49 cristal packages are outdated. There are smaller ones, such as
    SMU4

    Rene
     
  6. James Meyer

    James Meyer Guest

    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
     
  7. Ken Smith

    Ken Smith Guest

    Unless you are looking for a low noise crystal. Low noise crystals are
    still in the larger packages.
     
  8. Is it ok to substitute a crystal with a ceramic resonator for driving a
    I am no AVR specialist, but if the datasheet says it is possible it
    will be OK.
    HC49S is much smaller, even smaller than the ceramics I know, but of
    course the two capacitors spoil 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
     
  9. gwhite

    gwhite Guest


    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.
     
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