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LMX2594EVM: Evaluation module integer boundary spur and output power question

Shawn Workman
Genius 16020 points

Part Number: LMX2594EVM
Other Parts Discussed in Thread: LMX2594

Would someone provide some help regarding the LMX2594 evaluation module questions below:

 

The board is tuned to 7999MHz, with a 100MHz reference and a 100MHz PFD. The N divider is 79 and the fractional divider is 99/100.

This setup is using the evaluation module direct from the factory.

 

There are two questions in particular:.

1.       Regarding spurious performance of the part. It appears there is an integer boundary spur at 1MHz of about -68dBc. Does that seem accurate? There does not seem to be a spur specification in the EVM documentation or datasheet that seems to correlate.

2.       The output power at 7999MHz is about +2dBm. The datasheet says +5dBm is typical. Is that accurate?

Shawn

  • 0
    TI__Expert 5370 points
    Dear Shawn,

    two good questions.

    1) The spur found at 1 MHz is the integer boundary spur. at 1 MHz offset, the filter will have some filtering as the loop is likely about 300 kHz. -68 dBc is within what we would expect.
    2) On output power, +2 dBm is on the lower side. It depends on the setup. We have de-embedded cables and PCB losses to report +5 dBm. Is +2 dBm also taking cable PCB losses in consideration?

    Regards, Simon.