- Jan 1, 1970
Joerg said:3.5W at 11W out? Ouch.
Double-Ouch. I usually do SEPICs with the LM3478. About
a buck in quantities and that external FET ain't expensive
either. If it has to be dirt cheap I'll use a Schmitt
inverter. And it usually has to be dirt cheap.
I think a $1 LM3478 controller is better than a Schmitt
logic IC, but you're right, a small-die IC and a MOSFET
makes more sense than an expensive high-current part.
Especially when said part's switch dissipates so much
power. A decent MOSFET (looking for a cheap part) like
a 100V 0.1-ohm IRLR3410 (21.6 cents at DigiKey, 170,775
in stock, wow!) would only dissipate about 0.4 watts,
plus a little bit more for switching.
WRT using Google for engineering, presumably NSC would
be more interested in paying to promote their $4.95 part
(qty 500) on Google than a $1.10 part, but since Google's
"related pages" are not paid links, SFAIK, they used some
other rubric to pick the LM2587 IC instead of the superior
LM3478 + MOSFET, etc. Well, computers aren't too smart.