At 10:21 AM 2/13/2010, you wrote:
>Spehro Pefhany ha scritto:
> > 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.
>
>Yes, but .. ah ok: you mean:
>1) Dual Schottky
>2) LDO

Might be better to have a cap right at the LDO input.

>3) cap (already there anyway)

Make sure what you have meets the LDO output capacitance requirements.

It's pretty easy to make most LDOs oscillate if the capacitor is too small,
too large, or too good quality (low ESR), or in really bad shape (high ESR).

>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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