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In the KSZ8863 datasheet, the crystal specification is given (table 9-3), page 85.
Here the ESR is specified to 40ohms with no minimum nor maximum marking. Load capacitance is specified to a max of 20pF.
My Selected quartz has an 18pF load and 40ohms - which should fit the specification.
Calculation in this App Note shows that 2 capacitors of 22pF are fine for an equivalent 18pF load.
One drawback is the power dissipated (measured) in the crystal is ~150uW (nominal for that type is 100uW).
The next drawback is the gain margin for starting oscillation. By adding an additional resistor next to the crystal, the gain or negative resistance margin is calculated to be ~2, where commonly available sources refer to ~5.
Empirical try-and-fail shows that the current of the crystal can be easily reduced by changing primarily selected capacitors (2x22pF) to e.g. 2x10pF. BY changing that capacitor there is an improvement in gain margin too.
Appropriate crystal for 2x10pF load has ESR on the level of 60...100ohms.
The question is if the generator circuitry inside the Switch device will stable operate with a higher ESR of crystal. Any idea on the max value (similar to the 20pF max of CL)?
Here the ESR is specified to 40ohms with no minimum nor maximum marking. Load capacitance is specified to a max of 20pF.
My Selected quartz has an 18pF load and 40ohms - which should fit the specification.
Calculation in this App Note shows that 2 capacitors of 22pF are fine for an equivalent 18pF load.
One drawback is the power dissipated (measured) in the crystal is ~150uW (nominal for that type is 100uW).
The next drawback is the gain margin for starting oscillation. By adding an additional resistor next to the crystal, the gain or negative resistance margin is calculated to be ~2, where commonly available sources refer to ~5.
Empirical try-and-fail shows that the current of the crystal can be easily reduced by changing primarily selected capacitors (2x22pF) to e.g. 2x10pF. BY changing that capacitor there is an improvement in gain margin too.
Appropriate crystal for 2x10pF load has ESR on the level of 60...100ohms.
The question is if the generator circuitry inside the Switch device will stable operate with a higher ESR of crystal. Any idea on the max value (similar to the 20pF max of CL)?
