The RP511 from Ricoh Electronic Devices is a DC to DC Converter with Input Voltage 2 to 5.5 V, Output Voltage 1 1 to 4 V, Output Current 1 100 mA, Operating Temperature -40 to 85 Degree C, Storage Temperature -55 to 125 Degree C. Tags: Surface Mount, Buck/Step down. More details for RP511 can be seen below.