I found this formula to calculate the value of the capacitors for a crystal,
C(1,2)=2(CL-Cstray). C1 and C2 will use the same values. How do one choose the Cstray? I read that it ranges between 3pF~5pF.
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You don't choose \$C_{stray}\$.
\$C_{stray}\$ represents parasitic capacitance, mainly between the signal traces connecting the crystal to the rest of the circuit and ground (or whatever other low-impedance nodes are nearby).
The trick is, you generally don't know \$C_{stray}\$ very accurately. You have to estimate it from your trace lengths and geometry, and possibly adjust your added capacitors based on measurements after building your first prototype boards.
answered Nov 4, 2019 at 0:44