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Using Resonators with Propeller — Parallax Forums

Using Resonators with Propeller

william chanwilliam chan Posts: 1,326
edited 2009-01-12 06:02 in Propeller 1
Hi,

Can I replace my 5Mhz crystal directly with a 4Mhz resonator and just ground the middle pin?

Thanks.

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Comments

  • LeonLeon Posts: 7,620
    edited 2009-01-11 11:47
    Those three terminal ceramic resonators have built-in feedback capacitors. It would be better to use one without the capacitors (two terminals). Why don't you want to use a crystal?

    Leon

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  • william chanwilliam chan Posts: 1,326
    edited 2009-01-11 12:31
    Resonators are cheaper....
    I don't know why they are cheaper.

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  • Cluso99Cluso99 Posts: 18,069
    edited 2009-01-11 12:49
    They are cheaper but are not as accurate

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-01-11 17:49
    William,

    Cluso99 is correct. One place you may notice the consequences is with video output — especially composite color, which requires a very accurate timebase.

    -Phil
  • william chanwilliam chan Posts: 1,326
    edited 2009-01-12 03:50
    In my application, accuracy is not crucial.
    I just need to run faster than 20Mhz.

    In order to reduce the effects of the built-in capacitors in a 3 pin resonator, should i leave the middle pin unconnected?
    The Propeller datasheet seems to lack info on which types on resonators will work.

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  • LeonLeon Posts: 7,620
    edited 2009-01-12 06:02
    As the internal circuit of the resonator looks like this:

    
    --------X---------
      |         |
      C         C
      |         |
      ---------
           |



    You should be able to simply leave the ground connection disconnected. A two-terminal resonator would be cheaper, and more convenient, though.

    Leon

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