The RP539 from Ricoh Electronic Devices is a DC to DC Converter with Input Voltage 2.3 to 5.5 V, Output Voltage 1 0.6 to 5.5 V, Output Current 1 1000 mA, Operating Temperature -40 to 105 Degree C, Storage Temperature -55 to 125 Degree C. Tags: Surface Mount, Buck/Step down. More details for RP539 can be seen below.