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LMX2572: Integer Boundary Spurs not going away.

David Goins
Prodigy 30 points

Part Number: LMX2572

Im evaluating the LMX2572 with the TI EVM board and its 100MHz on board oscillator.

I want to create 4000.010MHz RF signal that doesn’t have integer boundary spurs.  What are the best R divider and multiplier settings to use?

Whatever dividers I use to move the integer boundary results in spurs similar or larger in size at roughly the same spots.  Basically I always have 10KHz IBS spurs on either side of the carrier at -40dBc.

  • 0
    TI__Expert 5370 points
    Dear David,

    I will go measure it and provide an update on this setting. need a day or two. It is likely that the integer boundary you have is with respect to the input reference OSCin in which case R or M will not help.

    thank you for your patience.

    Regards, Simon.
  • 0 in reply to Simon Damphousse
    Prodigy 30 points
    Thanks! Looking forward to you finding good results if possible. I usually put two independent references on board for this reason but there are frequency error differences on the two different references that cause problems in my applications. I wouldnt mind using the LMK61 to change reference frequency, but need 2.5ppm stability. I do have a temperature measurement on board, so if the LMK61 had monotonic frequency error with temperature, and was fairly repeatable across devices, I could compensate out freq error in the LMX2572. I have an email along these lines to my sales engineer, but havnt yet put that question to a forum...
  • 0 in reply to David Goins
    TI__Guru** 121510 points
    Hi David,

    I have forward the mail that I have responded to our sales regarding your question. Please check your inbox. I will close this post now.
  • 0 in reply to Noel Fung
    TI__Expert 5370 points
    thank you all, let us know if you have further questions...Simon.