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LMX2572: PLLatinumSIM MASH_Nonlinear Spur

user6249907
Intellectual 295 points
Part Number: LMX2572

In many cases, MASH_Nonlinear spur become the largest spurious in PLLatinumSIM SpurTips.

What is the principle of MASH_Nonlinear spur?

It's a bit of a painstaking process to find the MASH_seeds with the smallest supr by changing the Fnum and MASH_Order for all channel settings.

Is there any correlation between MASH_Nonlinear spur level and parameters like Fnum, Fden, etc.?

  • 0
    TI__Mastermind 28001 points

    Hi,

    This is not a simple topic to discuss, but here it goes ..

    The MASH_Linear spur can be calculated by taking the sequence of divides and calculating a Fourier series to find the spur levels.

    However, because the PFD/Charge pump is not perfectly linear, it causes spurs to be mixed back and come to lower frequencies.  So instead of spurs/noise theoretically going down as it gets close to the carrier, it instead approaches a noise floor.  This noise floor we measure and we add to the MASH_Linear to create the MASH_NonLinear one.

    Fnum, Fden, MASH_SEED, randomization, and Fractional order impact the MASH_Linear spur.

    Be sure to also click on all the "?" on the tool as it gives more information and context sensitive help.

    Regards,
    Dean