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TMS320F28384S: One question to crystal spec.

Luke Chen
Expert 5090 points
Part Number: TMS320F28384S


Hi champs,

In datasheet, F2838x support external crystal frequency up to 20MHz, can customer use 50ppm or 100ppm 20MHz crystal? Is there any limitation to crystal ppm?

The recommend load capacitance(CL1, CL2) range is 12pF - 24pF, does this capacitance value include PCB equivalent capacity or just for load capacitance?

Please advise your comments, thanks.

Regards,

Luke

  • +1
    TI__Mastermind 28275 points

    Hi Luke,

    You can use either a 50ppm or 100ppm crystal. Crystal ppms are usually very small and not a concern. It will be hard to find a crystal that has a ppm over 300 but even 300ppm only works out to 0.03% which is no problem for the device. The CL specification does not include PCB parasitic capacitance.

  • 0 in reply to Frank Ankapong
    TI__Expert 5090 points

    Hi Frank,

    Regarding external crystal spec., my customer would like to know the actual maximum frequency, how can we sure that even 300ppm crystal works for C2000?

    Please advise how to respond this question, thanks.

    Regards,

    Luke

  • 0 in reply to Luke Chen
    TI__Mastermind 28275 points

    Hi Luke,

    As I mentioned in my previous reply, 300ppm is 0.03% which is well within the margin of tolerance of the device. For perspective, the internal oscillator within the device (INTOSC) has a higher tolerance than any crystal you can get your hands on and the INTOSC also works fine with the device.