Does PLL VCCA require isolation if PLL isn't used?

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If the PLL isn't used is it acceptable to just tie this to 1.5V supply without the isolation?

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It`s not good.

Look at manual, there are 3 way to solve this task:

1. Separate VCCA Power Plane

2. Partitioned VCCA Island within VCCINT Plane

3. Thick VCCA Traces - I think it will good choice for you (The traces should be at least 20 mils thick, 3 capacitor, ferrite bead; loot at manual).

P.S: I saw some (cycloneI) board which were working without the isolation. You will able to risk if you want. IMHO 3 way it`s easy.