At 09:59 AM 2/13/2010, you wrote:
>Spehro Pefhany ha scritto:
> > I would suggest this is not prudent-- you *could* get flaky Ethernet
> > performance if the analog circuitry internal to the ENC does not have a
> > well-regulated supply. IIRC, only the digital circuitry has an internal
>
>Hmm, I see, this is a point indeed...
>Do you have any suggestion then?


The LDO is the way to go, maybe with a dual Schottky diode (eg. BAT160)
so only two parts total plus maybe a cap or two.

Keep in mind that if both power sources are present, and both are (nominally)
5V,  either one or both may be supplying current.


>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



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