STM8L151 crystal with Cload 20pF

[vzhan]

Dear,

according to the spec. of STM8L151, Recommended load capacitance C=CL1=CL2= 2*CLOAD of crystal, so, if the Cload is 20pF, we should use 40pF for CL1 and CL2?

please help to advise if it's ok and if have any other issues?

b/r

zhang

[Cristian Gyorgy]

Right!

To add the stray capacitance of the terminals and PCB tracks, the external capacitors can be approximated with: C1=C2=(CL-CS)·2, where CL is the load capacitance of the crystal given in the datasheet, and CS is the stray capacitance (3..5 pF or even higher, depending on your PCB design and crystal size).

For best results, start with this calculated values and than measure the resulting frequency and adjust the capacitors accordingly.

Good luck!