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  1. #1
    Full Member level 1
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    how to change crystal oscillator frequency?

    Hi~~
    i want to generate a 1.28MHz clock frequency.
    So i use this crystal oscillator
    http://www.txc.com.tw/download/o/ocxo_dip.pdf
    in pdf , it say the avalible frequency is 5~70MHz
    I want to generate a 5.12MHz frequency then divide 4 = 1.28MHz
    but how should i design circuit then the crystal can generate 5.12MHz?
    thank a lot ~~~!!!!

    •   Alt19th November 2006, 10:55

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  2. #2
    Advanced Member level 5
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    how to change crystal oscillator frequency?

    The standard oscillator outputs 10 MHz only. The PDF says 5~70 MHz is "available", but that means the factory can manufacture a special oscillator at your desired frequency within that range. Special-order oscillators usually cost extra money and time.

    You could design a PLL frequency synthesizer that converts 10 MHz to 1.28 MHz, but the phase noise may be significantly higher than an OCXO running at the desired frequency.

    Another possibility is to use a DDS (Direct Digital Synthesizer) that inputs 10 MHz and outputs a 1.28 MHz sinewave, followed by a square-wave converter. Maybe it will be clean enough for your application.

    Maybe you could use digital logic that simply drops cycles from the 10 MHz clock to give you 1.28 MHz, but that will have high jitter because the frequency ratio is not an integer.


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