[SI-LIST] Ferrite filter

Dear all,

I'm designing a board with a dual port Gigabit Ethernet Phy (Marvell
88E1020).
This device needs 3.3V and 2.5V power supply for analog core (and others for
digital core).
Marvell suggests using 3.3V digital power supply and filtering noise (caused
by other digital parts on board) by ferrite and caps to generate 3.3V for
analog. They also say that, without proper damping, you could have resonance
problems.
I can also generate 'analog' 3.3V (and 'analog' 2.5V) from 5V by a linear
regulator.
What is best:

- digital 3.3 + ferrite
- 3.3V from 5V by LDO
- 3.3V from 5V by LDO + ferrite ?

We also need other analog power supplies (for example PLLs...) on board.
Can we generate a single global analog 3.3V (from 5V by LDO) and use it for
PLLs, GbEthernet Phy and others ?

Thanks in advance and regards,

Silvano Bettinzana





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