Power Supply Rejection Ratio(PSRR)

C
The standard definition of PSSR is the log ratio of change in output voltage to change in input voltage of e.g. an operational amplifier or a voltage regulator.
This useless in your case. You are most probably interested in the change in oscillator frequency as a consequence of change in supply voltage. You can easily calculate the ration dFosc/dVsupply and use this as a definition for PSSR in your case. Note that unlike with voltages you cannot express this ratio in decibels because dFosc/dVsupply has a unit (Hz/V) wheras PSSR for an amplifier is unitless (units cancel when cyou calculate dVout/dVsupply).

I'm not sure whether that's the official definition - I know of none other.
 
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