loose-electron wrote on Aug 21st, 2015, 10:57pm:As the division of the feedback divider gets larger your phase noise gets worse.
Its effect is relative small.
My opinion is that both 800MHz and 3200MHz PLL give almost same in-band phase noise regarding fout=100MHz if PLL synthesizer is Integer-N.
However I expect 3200MHz PLL show better in-band phase noise if PLL synthesizer is Fractional-N.
And 3200MHz PLL has advantage about occupied area for loop filter, if charge pump current value is same.
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Lpll=Ndiv^2 * Lref
Lout=Lpll / Nout^2=(Ndiv/Nout)^2 * Lref
Lpll : in-band phase noise of PLL
Lref : in-band phase noise of reference clock, feedback divider and PFD.
Lout : in-band phase noise of fout=100MHz
(1) Ndiv=32, Nout=8, Ndiv/Nout=4
(2) Ndiv=128, Nout=32, Ndiv/Nout=4