On 11/13/2013 08:41 PM, Christopher Thomas wrote:

    On Wed, Nov 13, 2013 at 6:34 PM, luke.leighton

    <luke.leighton@gmail.com <mailto:luke.leighton@gmail.com>> wrote:
         > anyone any experience at dealing with that much power on
        small boards
         > (4 amp @ 5V) ?

          LM1084?  any guidance on PCB layout anyone aware of?

    Well, this will obviously be a 4 layer board, but I can say with the
    MEBv2, we had tremendous problems with thermal dissipation of the
    LM2576 at 9-12vdc, at 6vdc is was manageable, but the MEBv2++ are 2
    layer boards, and with the addition of a secondary power plane, it
    would probably have been fine. For the most recent versions, we are
    using an AP6503a, and so far at 6, 9,12 vdc the heat is
    non-existent. Not to mention, the local price of the AP6503 was .60c
    cheaper than the LM2576, and is 85-95% more heat efficient.


My point in mentioning the LM2576, is that they are functionally similar
to the LM1084, and both Linear.

CUI does board mount switching regulators that generate a lot less heat.

http://www.cui.com/product/power/dc-dc-converters/isolated/board-mount/20-w/pyb20-series

PYB20-Q24-S5 is an isolated supply that will output 5V at 4A.
But that digikey pricing suggests their not economical yet.

http://www.digikey.com/product-search/en/power-supplies-board-mount/dc-dc-converters/4325599?k=PYB20-Q24-S5