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Originally Posted by Rickertsen2
Thanks, i will go with a 10Mhz crystal x4 w/the PLL, like you suggested. Digikey sells 10Mhz fundamental mode crystals. Specifically i am loking at Digikey PN:X422-ND, X443-ND and XC953-ND. What is the difference? Which should i use? The X443-ND and XC953-ND specify 18pF load caps. The X422-ND just says "series" under load cap. What does that mean? Does this indicate that the crysta lis series cut rather than parallel cut? Also, if i ever want to use a third overtone crystal, do i use it like normal, or do i have to build a circuit that filters out the fundamental or something like that? Your help is GREATLY appreciated.
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James,
Again you have to really refer to the data sheet on the PIC. It describes a variety of oscillator circuits. When a crystal refers to capacitance it is referring to the maximum loading (capacitance in parallel with the crystal) that the crystal will oscillate reliably with. When the crystal is referred as series, it is cut to only work with series fed oscillator circuits. The PIC data sheet specifically calls for a parallel cut crystal or resonator. It also lists the crystals that were tested for various frequencies. Unfortunately none of your selection was on the list.
As you page through the catalogs and manufacturers websites, you will see crystals marked for overtone operation and the intended frequency range. The PIC data sheet has a lot of info. For other crystal oscillators you need to get a textbook to help you. I use the Radio Amatuer's Handbook (pub. Amateur Radio Relay League or ARRL) a lot for this kind of help and your library should have a recent copy as well as other electronics books on oscillator design and layout.