help with regulator selection

I might have suggested the lm series 2651 which obviously has to many legs :_) and runs a max of about 1.5 amps ..

TS1085CZ-3.3 (Taiwan Semiconductor)

Alternatively the LT1085 is a 3A adjustable output device in TO-220, but double the price.

Dave :)

Maybe I'm a tad slow, but having read all the descriptions there I didn't see anything that met the "specs". If you saw one for the job, can you point me at it please?

"budgie"

How low is that darn 5 volt rail gonna fall ??

......... Phil

there isn't really a 3 leg that will far as I know , but there are several solutions on the page that might get close dependant on the 5v rail drop .

No wonder, I was looking there for a drop-in 3-legged beastie.

The 5V is stiff as, good for 20A+. Droop is not an option.

I know there are manufacturers of *very* LDO units for lower currents, but haven't needed the higher capability until now.

National Semiconductor LM1085 / LM1084 might be usable too and are much cheaper than LT. Those are also in Farnell at least in the UK and probably in Australia too. I trust the LT part to stay stable under a wider range of conditions - the LM part has some worrying comments about capacitor ESR in the datasheet. It could be a trade-off between low price and a bit of tweaking vs. circuit working reliably first time at a higher price.

Chris