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

ehuang3190

Joined Jun 29, 2021
4

Papabravo

Joined Feb 24, 2006
17,551
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.

Attachments

• DickCappels and JohnInTX

ehuang3190

Joined Jun 29, 2021
4
Thanks for the reply! What exactly determines whether a crystal oscillates at the parallel or series frequency?

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
17,551
Also is R1 the same as the Equivalent Series Resistance, the L1 as Equivalent Series Inductance, and C0 the Parallel Capacitance?
Yes

• ehuang3190

ehuang3190

Joined Jun 29, 2021
4
Thanks! And I assume C1 is the plain Capacitance parameter?

Papabravo

Joined Feb 24, 2006
17,551
Thanks! And I assume C1 is the plain Capacitance parameter?

• ehuang3190

Papabravo

Joined Feb 24, 2006
17,551
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.

• ehuang3190