The US6K4 from ROHM Semiconductor is a MOSFET with Continous Drain Current -1.5 to 1.5 A, Drain Source Resistance 130 to 310 Milliohm, Drain Source Breakdown Voltage 20 V, Gate Source Voltage -10 to 10 V, Gate Source Threshold Voltage 0.3 to 1 V. Tags: Surface Mount. More details for US6K4 can be seen below.