The LM3401 is a switching buck regulator derived current source designed to drive a series string of high power, high brightness LEDs. The LM3401 controls an external P-FET, allowing the user to select a power device for the desired level of forward LED current. The LM3401 demo board can supply continuous current as high as 1.0A from an input voltage range of 4.5V to 35V. It is designed to operate at ambient temperatures up to 75°C.