Hi and thanks for the replies.
Obviously for 500mA+ apps, external power would be needed, as the USB can's do over 500mA, and probably won't even go over 400. I have a few 'wallwarts' switching and otherwise, and a 5v one would be convenient...but most I have are 9v, 500mA max. A 7805 would disipate 2W at full load (limited from the PSU) and would require a heatsink, ergo, profile.
That is, my board is of a stack design, so a vertical TO220 is too high, and a horizontal one..well...the heatsink would take up too much space. Its a double sided board, so a SO-08 underneath, with a few resistors and small caps is allowed. Any inductors, or larger caps would have to go on top though.
Hero999: good point, didn't think of that, so I guess the regulator doesn't need to take 'less than' 5V, I could just pass the USB power straight through for 5v, and use a 3.3v reg for, well, 3.3v
Outtolunch, I'm googling now, great response there, would be nice if I could get it down to a single IC.
Just DIY, good point, but this is for my own dev board, I'm bound to lose a wallwart and have to use another one, (say 9v?) and the 5v ones I've seen get expensive when the current gets to 1A. I do happen to have a switching reg of 10v @0.75A, would be nice to get 1.3A out of a SMPS at 5v.
Evandude: Excellent point, this is what i've been umming and arring about...is USB power good enough? well, it seems after your post and research, yes, it is
I'll just bypass the switching reg for USB apps, and have a jumper that selects between that and the output of a 3.3v reg.
I realise that 1-1.5A seems like a big deal, after all, for motor apps, I'll have a seperate power supply for a 'H-bridge module'. But I have a few LCD's whose backlights require a healthy 600mA, and they just look crap at 350mA. I'd say 95% of all I'll use this dev board for won't need more than 50mA, but its nice to have it there as and when I need it.....plus I've never build a SMPS before, like this dev board, its a learning experience as well as a handy thing to have.
Well advice taken on board (punn intended) I think I'll look for a relatively 'cheap' switching reg for 6-12V, so I can use more than 500mA from my 9v wallwart and any PSU I have right here, a jumper for USB power, and one for 5v/3.3v. I could have gone down the LM317 route, sure, but size and neatness, and the 'cool' factor
Just for kicks, I may look into an automatic 'USB power' switch, but that might be going too far, this is just a small 80x100m dev board after all.
Thanks again guys,
Blueteeth