PLL-comparison frequency

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ashutosh_g

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i have to design a 3.4GHz frequency synthesizer with a PLL.
i am using LMX2487 by national.. i dont have to switch my frequency (its not for wirless communication)

to reduce spurs i want to keep by comparison frequency as high as possible
in this if i use a crystal of 10MHz can i use it directly as phase detector frequency
waht will be the disadvantage of using such a phase detector freuequency ?
 

Hi Ashutosh
I would use as high a PSD freqeuncy as the chip will allow. You won't be multiplying the phase errors as much.
I'm not familliar with the National parts only AD. I don't think there is that much to choose between them, others may dissagree we all have our favourites ;->

If it is 3400MHz you want to generate try to get the PSD frequency up to 100MHz.

To analyse your PLL you could try ADIsimPLL from AD. it only simulates their parts but you could use it as a guide.

Peter
 

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