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LMX2594: spur

Amy Luo
Expert 6895 points
Part Number: LMX2594

Hi team,

The customer uses LMX2594 to output DAC sampling clock. The input of LMX2594 is 93.75MHZ, VCO = 12GHz, and the output is 6GHz. However, there is spurious at 3GHz. What is the possible reason?

In addition, other debugging conditions:

When VCO = 12GHz, VCO_PHASE_SYNC=1, the spurious frequency is 3GHz; After modifying the VCO frequency of LMX2594, the spurious frequency changes, but it is still VCO/4.

When VCO = 12GHz, VCO_PHASE_SYNC = 0, the 3 GHz spurious signal disappears.

  • 0
    TI__Mastermind 27981 points

    Amy,

    I think that the issue is that the SEG1_EN box is checked.  What this means is that there is an additional divide by 2 running that you do not need that is drawing current and producing a spur at 3 GHz.

    Try disabling this box.  I think that it will make your spur go away.