The FAN5606 LED driver generates regulated output currents from a battery with input voltage varying between 2.7V to 5V. An internal NMOS switch drives an external inductor, and a Schottky diode delivers the inductor's stored energy to the load. Soft start circuitry prevents excessive current drawn from the supply during power on. Any number of LEDs can be connected in series as long as the summed forward voltages do not lead to exceeding the specified operating output voltage range.