Question: How does CyClocksRT calculate cyrstal capacitance for the CY22050, CY22150 and CY22801? Should I account for board capacitance when entering a value?
Answer: When configuring clock generators for use with a crystal, CyClocksRT asks the user to enter a value for the crystal load capacitance rating (CL). It then calculates the appropriate device settings so that the crystal sees the correct load.
For the devices listed here, CyClocksRT assumes 2 pF of net board capacitance (4 pF per crystal pin).
Example: If you enter 18 pF, the software will configure the clock device for 16 pF net load to the crystal (32 pF per pin), with the assumption that the board contributes a net 2 pF (4 pF per pin).
If you determine that your board capacitance is greater than 2 pF (4 pF per pin), you should decrease the value you enter into CyberClocksRT accordingly.
Note that assumptions about board capacitance are not the same for all clock generator products.
