Texas Instruments TPS63000DRCT, 1 Buck Boost Switching, Buck/Boost Converter 1.2A, 1.2 → 5.5 V, 1500 kHz 10-Pin,

This highly efficient buck-boost converter uses a single inductor for DC to DC conversion. With automatic transmission between its Step Down and Step Up functions, buck-boost converters can be employed in battery powered products that use either a two-cell and three-cell alkaline battery, a NiCd or NiMH, or a single cell Lithium battery. This makes it ideal for use with cellular phones and similar hand-held devices.

DC/DC Switching Regulator Converters (Integrated Switch), Texas Instruments

The range of highly integrated high-efficiency switching voltage regulators from Texas Instruments includes Step-up (Boost), Step-down (Buck), Step-up/down (Boost/Buck) and Inverting types providing efficient solutions for every DC Voltage Regulator application.