LMX2581: LMX2581 Fractional Spur - Primary Fractional Spurs

Meng Liu

Part Number: LMX2581

Hi support team

l am reading LMX2581 datasheet and l am confused about primary fractional spur.

primary fractional spur is Fpd/PLL_DEN.For instance, if the phase detector frequency is 100 MHz and the fraction is 3/100, the primary fractional spurs would be at

1,2,4,5,6,...MHz..l want to know why n*Fpd/PLL_DEN, n don't choose 3.

over 4 years ago

0 Amin Eshraghi over 4 years ago

TI__Expert 6140 points

Hi Meng Liu,

I have assigned this to the right contact who will be in touch shortly.

Thanks and regards,

Amin

0 Vibhu Vanjari over 4 years ago in reply to Amin Eshraghi

TI__Genius 11900 points

Hello Meng,

The spur at 3 MHz would be an integer boundary spur. Refer to section 8.3.15.2 of the datasheet.

Thanks,

Vibhu

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LMX2581: LMX2581 Fractional Spur - Primary Fractional Spurs