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LMX2594: Clock Generator Query

Nireeksha Shetty
Prodigy 180 points
Part Number: LMX2594
Other Parts Discussed in Thread: LMK04828

Hi,

I'm using LMX2594 in my design for providing RF PLL to ADC and DAC.

As seen in my designs LMK (LMK04828) part is being used to provide input to LMX2594.Is there any specific reason why we need to use LMK clock generator.

Can we use any other clock generator in replacement of this for providing RF clock and input to LMX2594?

Regards,

Nireeksha

  • 0
    TI__Guru** 110620 points

    Hi Nireeksha,

    In addition to providing a reference clock to LMX2594, how do you use LMK04828?

  • 0 in reply to Noel Fung
    Prodigy 180 points

    Hi Noel,

    LMK I'm just using to provide reference clock to LMX and few other clocks such reference clock to DDR,ethernet etc

  • 0 in reply to Nireeksha Shetty
    TI__Mastermind 28560 points

    There is no requirement to use LMK04828 for LMX2594 reference.  The LMX2594 can use any clock source provided it's input specs such frequency and slew rate are met.  Also, generally higher frequency phase detectors will result in lower PLL noise, which typically dominates below the PLL loop bandwidth (reference noise also contributes below loop bandwidth).  The lower PLL noise may mean the loop bandwidth may be widened to reduce total jitter.

    • So depending on the frequency and performance of your reference, loop bandwidth for optimum jitter may change.

    To get an idea of all this, the PLLatinum Sim software can be used (https://www.ti.com/tool/PLLATINUMSIM-SW) can be used simulate performance.

    • If you measure the phase noise profile of your reference
    • Then use that phase noise profile and frequency as reference noise in PLLatinum Sim to see how the performance may be different to the performance you get with the LMK04828.

    73,
    Timothy