I've reviewed all the FAQ's and documents that I could find on the web but unfortunately I still believe I am missing information on calculating the correct loading capacitance for my crystal.
I am using a 18.432MHz crystal on my AT91SAM9261 and I want to be sure that the loading capacitors are exactly correct so that my system starts up every time and the crystal is oscillating at the correct frequency.
When I reviewed how the pierce oscillator works and I want to calculate the resultant load capacitance. I need to know the internal load capacitance of the XOUT and XIN pins of the AT91SAM9261.
Here is a link to the datasheet of the crystal I am going to be using. The crystal has a load capacitance of 16 pF.
Here is a link to the datasheet of the AT91SAM9261. See page 673 for the main oscillator:
According to my layout guy the capacitance on the traces connected from my crystal Y1 to the AT91SAM9261 is < 1 pF.
Y1.2 0.71 pF Y1.1 0.36 pF
What value of capacitance should I use for the external load capacitance to ensure my boards startup every time and the frequency is accurate. What percentage of tolerance should I use on the caps?
Thank you so much!
-E