What does each parameter for crystal oscillator mean in LTSpice? Trying to make a 13.56 MHz crystal oscillator

Thread Starter

ehuang3190

Joined Jun 29, 2021
4
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Do they correspond to some of the parameters here? In particular does the capacitance refer to C1, or is it load capacitance? What exactly is load capacitance anyway? Thank you!
 

Papabravo

Joined Feb 24, 2006
17,240
It just so happens that the Capacitor component (C) can be used to model a crystal. The component values are called "motional parameters" because they model the mechanical response of the "cut" crystal.. Crystals actually have two resonant frequencies. The lower one is called the series resonant frequency and the higher one is called the parallel resonant frequency. You can also use arbitrary combinations of ideal L's, R's, 'n C's to simulate a crystal. L1 and C1 determine the series resonant frequency. R1 determines the loss and thus the Q of the crystal.

Below are examples of some simulations
In the first one the values for 100 kHz are explicit
In the second one the values are in the subcircuit which I have included on the schematic. I don't have a model for 13.56 MHz, but creating one should not be difficult.
 

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Thread Starter

ehuang3190

Joined Jun 29, 2021
4
Also is R1 the same as the Equivalent Series Resistance, the L1 as Equivalent Series Inductance, and C0 the Parallel Capacitance?
 

Papabravo

Joined Feb 24, 2006
17,240
Thanks for the reply! What exactly determines whether a crystal oscillates at the parallel or series frequency?
Without additional external capacitance a crystal will tend to oscillate at the series resonant frequency. The external capacitance can pull the crystal toward the parallel mode.
 
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