# How do I choose the correct capacitors to use with my Crystal?

I am looking at using this crystal for a new circuit design. It will provide the main oscillator for my PIC application.

Here is the part on digikey.

The datasheet indicates that it has a load capacitance of 8pF. This seems very low compared to most. I have read that the load capacitance should be equal to:

$$\frac{(C_1\times C_2)}{(C_1+C_2)} +C_{stray}$$

where Cstray is the capacitance of the PCB traces which are typically between 5 and 15 pF.

This equation is provided in a Microchip FAQ sheet. If this is correct my PCB trace capacitance is likely already equal to the load capacitance of the oscillator. So does this mean that I really don't need any capacitors connected between the crystal and ground?

• Dec 13 '10 at 15:30