Mayank
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Hello Boa, If Area is not a major concern, you should give your Oscillator a separate supply with an extra LDO maybe....If your area doesn't permit a separate LDO, atleast route the VCO supply separately & directly from PMU input. If spurs are not a major concern, then you can club together CP & PFD into same supply to avoid ESD concerns, level shifter noise etc., else club PFD and dividers together into digital supply.....On-Chip Loop Filter is preferred as it prevents extra transmission line delay+noise to get added to the circuit...To prevent re-spin as cmos_cowboy pointed out, introduce some programmability for Loop Filter...
--Mayank.
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