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Original question:

LMX2571: LMX2571 SPUR-B-GONE ALGORITHM

LMX2594: creating a SPUR-B-GONE ALGORITHM for LMX2594

Thomas Noonan
Prodigy 140 points
Part Number: LMX2594
Other Parts Discussed in Thread: LMX2571, LMX2572

I am looking to use the LMX2594 on my next project and would like to incorporate the equivalent of The Spur-B-Gone algorithm into our code controlling the synthesizer.  On July 23rd Dean Banerjee posted the code from TICS Pro in his response to   "LMX2571: LMX2571 SPUR_B_GONE ALGORITHM".  It looks like the code was written in Python but there are no indentations and I'm having trouble following the loops in the code without them.  Can you re-post the code with the indentations.

Thanks,

Tom

  • 0
    TI__Mastermind 28011 points
    Thomas,

    The actual code for the PLL GUI can be found in the install directory under:

    TICS Pro\Configurations\Devices\PLL + VCO\LMX2571

    The code that actually runs the LMX2571 is called "LMX2571_PLL.py". This contains the Spur-b-Gone Code.

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    Prodigy 140 points

    Dean,
    Thank You.
    I do have a quick follow up. Is there a reason that only the LMX2571 has Spur-b-Gone in TICS Pro or future updates incorporate it.

    Thanks Again,
    Tom

  • 0 in reply to Thomas Noonan
    TI__Mastermind 28011 points
    Tom,

    The Spur-b-Gone algorithm could be used for the LMX2594 and all devices. However, the programmable multiplier (MULT, not OSC_2X) adds 8 dB to the figure of merit to the PLL. Also, there is a spur formed by the output mixing with the input Fout%Fosc that is not reduced by the programmable multiplier.

    The programmable multiplier has it's place and time, but it's not a free lunch and some situations are less effective than others. For devices that do not have an external pull-up on the outputs, the programmable multiplier is more effective on spurs. For instance, the multiplier is also most effective on the LMX2572 as it does not have pull-ups on the outputs and has better Fout%Fosc spurs.

    Regards,
    Dean