Hi guys,

Does anyone have a favourite 5V/5A switch-mode PSU controller chip?

I'm designing the PSU section of an FPGA-based device that needs 5V (for =

some pull-up resistors and LSTTL), 1.2V (FPGA Vcore), and 3.3V =

(everything else). The 3.3V and 1.2V supplies are generated by a Texas =

Instruments TPS75003 SMPSU controller.

I was thinking about just using a 5V external, but then I started =

wondering about the possible effect of Sod's Law on my device:
   - If I use a standard connector (5.5x2.5mm coaxial DC power jack) =

then what happens if Joe "Dumb" User plugs in a 12V supply from =

something else? Obvious answer is "big frickin' boom".
   - It seems most DC plugpacks are either 4.5V, 6V or something higher, =

and typically top out at 12V.

So I'm contemplating rigging the thing to take an input of 12V, then =

step that down to the 5V needed to run the TPS chip. But what I need is =

a chip to do that, and all the ones I've found are incredibly expensive =

(the TPS chip is =A32+VAT; the 5V/5A chips I've seen are =A36 and up).

Does anyone have a favourite SMPSU chip that meets these criteria?
   - 12V (preferably up to 15V) input
   - 5V output, 5A (25W)
   - Low total cost, few external parts (I can live with an external =

power FET)
   - ~65% or better efficiency

I've seen the NatSemi Simple Switcher chips (LM22677/8), but these seem =

to be "just a bit" on the expensive side for what they are.

The other option I thought of was to use an MC34063 with an external FET =

or BJT.... but AIUI that's going to be about as efficient as a 7805. :-/

Thanks,
-- =

Phil.
piclist@philpem.me.uk
http://www.philpem.me.uk/

-- =

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