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Generating a 180MHz low jitter clock output from a single crystal oscillator

Marius Jansen van Rensburg
Prodigy 210 points
Other Parts Discussed in Thread: CDCM61001

Hi All,

I have absolutely no experience in clock generation so I was wondering whether the following can be achieved (and what would be the best way to do so):

  • Would it be possible to generate a 180MHz, low output jitter, LVDS clock signal from a single common value (8-32MHz) crystal oscillator?
  • What would be the best starting point for such a solution?
  • This will be for experimental purposes, so there is no limitation on the part count / cost.
  • Can the above LVDS output be further improved by running it through a clock jitter cleaner?
  • Is such a solution possible without a digital interface to the clock generator (i.e. can the output frequency / dividers be set using external passive components?)

This clock source will be used for a high speed DAC.

Any feedback would be greatly appreciated.

Regards

Marius 

  • 0
    TI__Mastermind 32575 points
    CDCM61001 is a pin-configurable clock generator that can use a 24 MHz crystal resonator or oscillator (XTAL or XO) input to lock the internal VCO to 1800 MHz, and output 180 MHz with integer output divider.

    The pin configuration settings to achieve your frequency plan is:

    PR[1:0] = 2'b01 --> PLL Prescaler divider = 5, PLL Feedback divider = 15
    OD[2:0] = 3'b001 --> Output divider = 2
    OSC[1:0] = 2'b01 --> LVDS output

    Fout = (FBDIV / OUTDIV) * Fin = (15 / 2 ) * 24 MHz = 180 MHz

    This application report should give you an idea of the phase noise performance using a crystal input with different output frequencies (see 187.5 MHz output phase noise performance should be fairly representative of 180 MHz you need).
    www.ti.com/.../scaa099.pdf
    www.ti.com/.../scaa100.pdf

    Regards,
    Alan
  • 0 in reply to Alan O
    Prodigy 210 points
    Hi Alan,

    Much appreciated. I have long considered the TI E2E Support Forum to be one of the best online design resources. This was again confirm today from your quick and detailed reply. Thank you very much.