load capacitance CL XTAL

[ArCoN]

Hi All

I'am a little confused by this.

Does CL means the xtal have that load or does it mean they recommends to load with that value?

https://www.jauch.com/downloadfile/5887342ab8f56_49fb800c54cda51a6f44/jxs22wa-20161222.pdf

driver spec attached

Can i skip CL if the xtal is in spec with the driver?
I'am tight on space

Thanks

[Niklas]

No, you will need the load capacitors and probably also a small series resistor to adjust the drive level to be approx 10uW. ST has a document that describes how to calculate what load capacitance you will need, see link below, but you will have to check the gain margin from the IC that you are planning to use. The series resistor will limit the power dissipated in the crystal so it does not exceed the maximum of 100uW stated in the datasheet. Many older, physically larger, crystal could handle more power, so then it was not that big issue to skip the resistor.

www.st.com/content/ccc/resource/technical/document/application_note/c6/eb/5e/11/e3/69/43/eb/CD00221665.pdf/files/CD00221665.pdf/jcr:content/translations/en.CD00221665.pdf

[duak]

If you want the crystal to oscillate at its specified frequency you have to provide the correct CL.  If you look at the equivalent circuit for a crystal, eg. https://en.wikipedia.org/wiki/File:Crystal_oscillator.svg you can probably see that the value of CL helps determine the actual frequency.  If the exact frequency doesn't matter, you might be able to work with what you have.

I once ordered some custom crystals for a timebase oscillator that oscillated a few hundred Hz off that of the desired frequency and there was no way I could correct it.  I went back to the order form and saw that I had specified the wrong circuit.  Oooops!

Cheers,