The FAN5608 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. Proprietary internal circuitry continuously monitors each LED current string and automatically adjusts the generated output DC voltage to the lowest minimum value required by the LED’s string with the highest summarized forward voltage. This adaptive nature of the FAN5608 ensures operation at the highest possible efficiency. 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. Although it is not required to have an equal number of LEDs connected in series within each branch, the highest efficiency and best current regulation is always achieved when an equal number of LEDs are serially connected.