The SPF1K5S3R3 from Calex Manufacturing is a DC to DC Converter with Input Voltage 4.5 to 5.5 V, Output Voltage 1 3.3 V, Output Current 1 260 mA, Output Power 1 W, Isolation Voltage 3 kV. Tags: Through Hole, Buck/Step down. More details for SPF1K5S3R3 can be seen below.