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LMK61E2: difference between setting the NUM/DEN as 17/1536 and 17000/1536000

Part Number: LMK61E2

Hi expert,

I would like to know the performance different between setting the NUM/DEN as 17/1536 and 17000/1536000. Does 17000/1536000 push the fractional spur energy to higher frequencies for better filtering?

Thanks.

  • Hi Di, 

    I tested this on the LMK61E2EVM at ~100 MHz and I didn't notice any significant difference in phase noise between the two configurations. If you have some register profiles available I can test those on the EVM as well. The device will have better performance in integer PLL mode rather than fractional, but if the fractional mode is being used the exact values of NUM and DEN should not have a major impact on performance.  

    Regards, 

    Connor 

    17/1536 profile:

    17000/1536000 profile: