The LM3404/04HV is a buck regulator derived controlled current source designed to drive a series string of high power, high brightness LEDs (HBLEDs) such as the LuxeonTM K2 Emitter at forward currents of up to 1.0A. The board can accept an input voltage ranging from 6V to 42V when using the LM3404. When using the pin-for-pin compatible LM3404HV the upper bound of input voltage is 75V. The converter output voltage adjusts as needed to maintain a constant current through the LED array. The LM3404/04HV is a true step-down regulator with an output voltage range extending from a VO (MIN) of 200 mV (the reference voltage) to a VO(MAX) determined by the minimum off time (typically 300 ns). It can maintain regulated current through any number of LEDs as long as the combined forward voltage of the array does not exceed VO(MAX)..