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Crystal options for AM335x

Hi,

I am currently investigating crystal solutions to use with the AM335x in our design.  We have an existing 25MHz crystal we would like to reuse however its shunt capacitance is 7pF which is above the recommended maximum of 5pF (SPRS717C page 97).  I noticed in another forum post on the DM8148 that the shunt capacitance requirement could be relaxed to 7pF (http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/103408.aspx).

The crystal we would like to use is a Fox FQA part (http://foxonline.com/pdfs/fqa.pdf) with a specified load capacitance of 20pF.  Could we use this crystal with the AM335x? or is there another crystal you could recommend?

Kind Regards

Mark

  • I recommend you use a crystal that meets the data sheet requirements.

    Your FOX FQA 25MHz crystal may actually meet this requirement.  The data sheet you referenced is for the entire FQA series which has a very wide frequency range.

    Crystal manufactures provide these one page data sheets with max parameters that cover the entire series, but in reality they can provide more refined specifications for specific part numbers.

    If you contact Fox and ask them to provide specifications for your specific crystal part number, you may find the 25MHz version has a shunt capacitance less than 5pf.

    Regards
    Paul

  • I can't help but notice the Sunstsu SCC series crystal used on the AM335x eval board has a max shunt capacitance rating of 7 pF as well.  Is this a similar case where TI verified the the specific crystal used is within the AM335x datasheet spec despite the crystal series shunt capacitance spec being greater than 5pF spec?