Hi,
I do not see any information about the Shunt capacitance and C1/C2 values for the 38.4MHz ceramic resonator. Can I please have this information?
Digikey part no : 490-XRCGB38M400F1S2GR0TR-ND
manufacture part no : XRCGB38M400F1S2GR0
Thank you for your inquiry.
Firstly, I believe you have a Crystal Oscillator here, not a Ceramic Resonator.
Manufacturers rarely provide the C1/C2 values because the amount of stray capacitance designed into the circuit board needs to be spit into the equation.
I wrote on the subject of Load Cap Selection on a TechForum post here
Based on the above TechForum post the formula I have:
Load Cap value = 8pF
( 2 x Load Capacitance of Crystal ) - Stray Capacitance
(2 x 8pF) - 5pF < - Assumed Stray Capacitance
16pf - 5pF = 11pF
If you want to be super safe, plug into the circuit of the crystal every cap value close to 11pF and document when the part fails, and then use a capacitance value directly in the middle of the low and high values of failure.
I’m basing my equation on Atmel’s (now Microchip) AVR042 Application Note
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Can you confirm its a crystal? Because I see the same Mfr Part no: on the mouser Site and it says resonator .
And this was the only datasheet I found. The resonator is expected to have the caps within it, which isn’t specified in the datasheet. And when the load cap is mentioned to be 8pF, without knowing the internal cap load (C1/C2) We cannot balance it out while mounting external caps for resonance.
So I need to place (2x 8pF) - 5pF(Stray) - ( Internal C1/C2) but I do not know C1/C2.
Also could you lead me to 38Mhz Resonator part no:?
Murata Electronics calls it a Crystal Unit and indicates the element is made of Quartz. They are confusing things a little because they also refer to them as Resonators but everything in the datasheet leads me to believe this is to be treated as a Pierce Oscillator.
C1 and C2 are the answer to the (2 x 8pF) - (5pF stray capacitance) equation. They would be external caps that need to be added to the Crystal.
I don’t see that we have any 38MHz or 38.4MHz frequency Ceramic Resonators.