power supply question

[harrybissell at prodigy.net]

Usually a bad idea. Most dual supplies either switch one out (like a normallized jack) or use diode or gates so the higher voltage wins. This causes .6V drop which can be a problem (esp on a 5V supply thats 10% loss.) Shottky diodes have smaller forward drop... better


 ---- On Mar  9 "Roel Das" <Roel.Das at student.groept.be> wrote: 
> Does it hurt if you connect an external power supply to a device, after it's
> own voltage regulator circuit?
> I want to use an external power supply on Atmel's STK200, is it okay to just
> connect the ground and 5v of the external power supply to some of the
> STK200's gnd and 5V out?
> I does work, but does it hurt the internal power circuit?
> 
> Thanks
> Roel
>