Hi,
I don't like to waste topics/posts with 'pointless' questions, but I have googled this one, and the number of results from maxim/national semiconductor are just overwhelming, so I hope someone could help me narrow down the search.
I'm designing a dev board for PIC (and AVR's ) and I would like to have a switching buck regulator to reduce the profile of the voltage regulator section (or area if its horizontal), and to negate the need for a bulky heatsink. Since its a modular design, any 'modules' attached will draw their power from the boards supply, so 1-1.5A max. is needed. A simple 7805 is out of the question here.
Now, What I would *like* is the ability for it to be powered either by external DC (6-?v) OR USB power. And outputs 5v or 3.3v depending on a jumper setting/switch. The problem is, that, USB doesn't always provide 5v exactly, so it could be possible that the regulator would have to 'boost' the voltage ever so slightly for 5v apps, or at least pass it through. So I guess the input should be from 4.8v (ish) to say, 12/15V.
I realise I could make my life a lot easier if I just have three jumper settings:
external 6-12V to regulator - 5v...with a jumper setting to switch this to 3.3v. And USB direct power, with a setting for 'USB direct or 3.3v reg'. That would require two regulators, one for 5v and one for 3.3v. Ok, so thats 4 settings, 2 for input, and 2 for output. 3.3v is needed, because level shifters (bidrectional) seem to be pretty expensive.
As always I tend to vastly overcomplicate things, so any advice would be helpful.
Regards,
Blueteeth
I don't like to waste topics/posts with 'pointless' questions, but I have googled this one, and the number of results from maxim/national semiconductor are just overwhelming, so I hope someone could help me narrow down the search.
I'm designing a dev board for PIC (and AVR's ) and I would like to have a switching buck regulator to reduce the profile of the voltage regulator section (or area if its horizontal), and to negate the need for a bulky heatsink. Since its a modular design, any 'modules' attached will draw their power from the boards supply, so 1-1.5A max. is needed. A simple 7805 is out of the question here.
Now, What I would *like* is the ability for it to be powered either by external DC (6-?v) OR USB power. And outputs 5v or 3.3v depending on a jumper setting/switch. The problem is, that, USB doesn't always provide 5v exactly, so it could be possible that the regulator would have to 'boost' the voltage ever so slightly for 5v apps, or at least pass it through. So I guess the input should be from 4.8v (ish) to say, 12/15V.
I realise I could make my life a lot easier if I just have three jumper settings:
external 6-12V to regulator - 5v...with a jumper setting to switch this to 3.3v. And USB direct power, with a setting for 'USB direct or 3.3v reg'. That would require two regulators, one for 5v and one for 3.3v. Ok, so thats 4 settings, 2 for input, and 2 for output. 3.3v is needed, because level shifters (bidrectional) seem to be pretty expensive.
As always I tend to vastly overcomplicate things, so any advice would be helpful.
Regards,
Blueteeth