Maxim Integrated Products introduced the MAX1836/MAX1837, which are the smallest step-down DC-DC converters with an internal 24V P-channel MOSFET switch. They come in 6-pin SOT23 packages to save space and allow direct conversion from +24V inputs, eliminating the intermediate step-down voltage that wastes over 15% of the battery life and increases complexity. Applications include I/O, audio, and video supplies in notebook and handheld systems powered by up to 4 Li+ batteries and AC/DC adaptors.

The MAX1836 delivers up to 250mA, and the MAX1837 delivers up to 125mA, permitting optimal selection of the inductor. Efficiency is 90%, and quiescent supply current is a low 12µA (3µA in logic-controlled shutdown). They also include current-limiting and overtemperature protection.

The story here is the size. The real estate used by the SOT-23-6 is certainly the smallest footprint that is available for a conversion from higher than 15 V down to 3.3 V. I am unable to comment on the claimed 90% conversion efficiency because no data sheet was available on Maxim's web site -- even though the data sheet for the parts' evaluation kit is: Bizarre.

Nice consumption numbers and the choice of either 250 or 125 mA loads in the two parts offered is a compelling range for the likely applications. I also like that the company has been able to include current limiting in a 24-V part.