Crystal oscillator tied to supply voltage?

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  1. - 26th March 2009, 15:22 #3
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    Gusse
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    I think both ways are OK. More important is to understand, which is more noiseless: Vdd or Vss. You should always try to minimise noise, which can couple to XTAL.

    If decoupling to Vss (=GND) is sharing common impedance with some other high current source, then it might be wiser to connect XTAL caps to Vdd. This requires that PDN (power delivery network) has a low impedance also at XTAL frequencies and above. Might require some capacitor optomizations...

    Normally GND potential has lower noise level than power supply, but not always. Basic EMC!

    BR,
    -Gusse-
    Last edited by Gusse; - 26th March 2009 at 15:25.
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