The MP4000 is a high efficiency step-down converter designed for driving high brightness LED. The MP4000 drives an external MOSFET in the floating buck converter structure. The inductor current is regulated with boundary conduction mode which features no reverse recovery loss in the freewheeling diode and soft turn on for the power MOSFET. Such operation mode can achieve very high efficiency and at the same time minimize the inductor value and size. Also,the LED current can be well regulated by controlling the MOSFET peak current, which is sensed through an external resistor. Its low 300mV feedback voltage reduces power loss and improves efficiency.