Seb, it's yours design so you have to enlighten us. You want three power supplies: one battery, one external supply, one USB. The load is one nanowatt PIC and one XBEE which draw max 270mA on TX and the user unknown load. In your opinion the 500mA fuse should protect the load for the extra drawn current, the power supplies or all of them?
Vasile On Sat, Feb 5, 2011 at 5:00 AM, Sebastien Lelong <[email protected] > wrote: > Or, should I keep another fuse at its first place, after regulation ? I > first thought that put this fue here would protect USB (but not the > regulation part) and the whole circuit. > > Please enlighten me ! > > Seb > > 2011/2/5 Sebastien Lelong <[email protected]> > > Hi Kiste, >> >> 2011/2/5 Oliver Seitz <[email protected]> >> >> >> Both USB and U1 have short circuit protected outputs. >>> >>> You mean, power rails on USB connectors at a computer are short-circuit >>> protected? This is true, but the protection is often a non-resettable SMD >>> fuse somewhere in the middle of a very big PCB called mainboard... I'd >>> prefer not to blow that one. >>> >> >> :) >> >> OK, so I can put another SMD fuse for USB. >> >> >The trouble with polarity protection (this is what we're talking about >>> isn't ?) is the drop voltage involved with diode. >>> >>> Only if you're using a diode in series. You could also use the fuse and a >>> reasonably strong schottky diode from ground. So, reverse polarity will not >>> go beyond 0.5V, and the fuse will blow when strong reverse power is applied. >>> >> >> Thanks for the tip. Could you point to some direction about this diode ? >> >> I was also thinking about using a schottky diode to regulate max 3.3V. I >> mean, according to my last power supply schematic, if user select USB but no >> regulation, xbee could be damaged for instance. Could a 3.3V schottky diode >> be used for thi purpose ? (make sure it won't be more than 3.3V ?) >> >> >> Cheers, >> Seb >> > > > > -- > Sébastien Lelong > http://www.sirloon.net > http://sirbot.org > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<jallib%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/jallib?hl=en. > -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
