Самое высокое КПД, до 93%, у LM5165 : 3V-65V, 150mA Synchronous Buck Converter With Ultra-Low IQ; 0.5 USD. У LM5008 (КПД 66%) 9.5-95V Wide Vin, 350mA Constant On-Time Non-Synchronous Buck Regulator, доставабелен по 100+ р. http://www.elitan.ru/price/index.php?find=LM5008&delay=-1&mfg=all&seenform=y&utf=1
http://www.ti.com/product/LM5165
http://www.ti.com/product/LM5008