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Recommended crystal oscillator 28026 or 28035

Gary H
Expert 1855 points

Other Parts Discussed in Thread: TMS320F28026, TMS320F28035

 

I am using the TMS320F28035 currently and my change to the TMS320F28026 at a later date.

I need my 60MHz clock to be as accurate as possible and have as little temperature drift as possible.

My list of questions are:

  1. I assume the best way to do this is with an external oscillator or crystal. Is this true?

  2. If yes, can you recommend a manufacturer to contact to help choose the best external solution.

  3. I assume if I use an external crystal or oscillator, I do not need to use the internal temperature compensation. True?

  4. Assuming I have a perfect external clock source. How much error does the internal phase lock loop add to the clock error at 60MHz?
  5. What frequency external source should I choose to get the most accurate 60MHz sysclock?

I would appreciate any help in this area.

 

  • 0
    TI__Guru 60865 points

    1. Yes.  Best case with internal oscillator + compensation is +/-1% frequency accuracy.  An external oscillator can be much better. 

    2. I don't think we have a pre-packaged solution.  I would recommend positing another question which asks other users what specific parts they have used successfully.

    3. Correct.  Compensation is only for internal oscillators.

    4. This can be estimated for the F2803x and F2806x device families as roughly 

    Jitter = MAX ( [input-clock-jitter], [pll_output_clock_period*0.05*sqrt(2)])

    Where all the parameters (jitter, input jitter, and output clock period) are in units of absolute time. 

    5. If you want 60MHz, I think you have to use the PLL. I don't think it matters in this case which way you get to 60MHz.  You can bypass the PLL completely, but only up to 30MHz.