The LM3421 and LM3423 family of devices are versatile high voltage N-channel MOSFET controllers for LED drivers. They can be easily configured in buck, boost, buck-boost and SEPIC topologies. This flexibility, along with an input voltage rating of 75 V, makes the these controllers ideal for illuminating LEDs in a large family of applications. Adjustable high-side current sense voltage allows for tight regulation of the LED current with the highest efficiency possible. The LM3421 and LM3423 devices use predictive off-time (PRO) control, which is a combination of peak current-mode control and a predictive off-timer. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation. The LM3421 and LM3423 devices include a high-voltage start-up regulator that operates over a wide input range of 4.5 V to 75 V. The internal PWM controller is designed for adjustable switching frequencies of up to 2 MHz, thus enabling compact solutions.