2011/2/5 vasile surducan <[email protected]> > > I'm not happy too with this. I thought about this a lot, without good >> results as you can see. I could remove external source, thus removing JP7. >> > > one compromise: use a three pole jumper, either JP3 or JP7 by one move... >
I'll try ! > > >> >> >>> but that is, usually the fuse is protected by the micro or by the >>> regulator, however one smd fuse (thermal or breackable) is enough, but I'm >>> afraid yours will not protect something... >>> >> >> So where do you suggest to put it ? BTW symbol is resettable but I'm >> planning to use "real" smd fuse. >> > > There are two unprotected power supplies: the battery which is most > aggressive since a short circuit current can go higher than 500mA and the > external power supply. Both USB and U1 have short circuit protected outputs. > since you choose to protect only 3V3, then the logic place is in series > with external battery. However, there is no reverse voltage protection > neither for batter nor external power supply which is bad... > The trouble with polarity protection (this is what we're talking about isn't ?) is the drop voltage involved with diode. For external power supply, it'd be ok, but for battery, for which I plan to use 2 x AAA cells, I just can't afford it... The difference between battery and external is just external goes to the 3.3V regulator. I could remove external and put a jumper to select whether to go to the vreg or not. thi would give something like this: [image: power.png] Obviously, the problem is now when you put more than 3.3V (or more) and select no regulation... Maybe I could combine both 2-way jumpers and physically avoid some combination (cut wire, something like that), so when you select USB, at least you have to choose regulation. Would fuse be properly set in this case ? Cheers, Seb -- 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.
<<power.png>>
