The 51028121 from Frontgrade Technologies is a DC to DC Converter with Input Voltage 21 to 38 V, Output Voltage 1 12 V, Output Current 1 0 to 4.2 A, Output Power 0 to 50 W, Operating Temperature -55 to 125 Degree C. Tags: Surface Mount, Buck/Step down. More details for 51028121 can be seen below.