[SOLVED] Crystal Load Capacitor

[Techman_7]

For microcontroller crystal oscillator, as in below snap.

To calculate the load capacitance following formula is used -

where, Cs = PCB stray capacitance.

Now, here are Cx1 & Cx2 in series with each other? If they are in parallel, it will be Cx1 + Cx2.
Can anyone pls let me know about Cx1, Cx2 series combination & HOW they are in series ?

 

[KlausST]

Hi,

the loop of the resonance circuit is: GND --> CX1 --> XTAL --> CX2 --> GND

Cs is PCB stray capacitance + input capacitance of XTAL1

There are plenty of application notes around explaining the circuit. I guess every XTAL maunfacturer provides them for free and with very good quality. (Because they want to sell their XTALs)

Klaus

 

[danadakk]

https://www.ti.com/lit/an/szza043/szza043.pdf?ts=1676648753511&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.edn.com/crystal-oscillator-fundamentals-and-operation-part-ii/

https://ecsxtal.com/store/pdf/Oscillation-Circut-Design-Considerations.pdf

Regards, Dana.