LM3424,pdf datasheet (Constant

The LM3424 is a versatile high voltage N-channel MosFET
controller for LED drivers . It can be easily configured in buck,
boost, buck-boost and SEPIC topologies. In addition, the
LM3424 includes a thermal foldback feature for temperature
management of the LEDs. This flexibility, along with an input
voltage rating of 75V, makes the LM3424 ideal for illuminating
LEDs in a very diverse, large family of applications.
Adjustable high-side current sense voltage allows for tight
regulation of the LED current with the highest efficiency possible.
The LM3424 uses standard peak current-mode control
providing inherent input voltage feed-forward compensation
for better noise immunity. It is designed to provide accurate
thermal foldback with a programmable foldback breakpoint
and slope. In addition, a 2.45V reference is provided.
The LM3424 includes a high-voltage startup regulator that
operates over a wide input range of 4.5V to 75V. The internal
PWM controller is designed for adjustable switching frequencies
of up to 2.0 MHz and external synchronization is possible.
The controller is capable of high speed PWM dimming and
analog dimming. Additional features include slope compensation,
softstart, over-voltage and under-voltage lock-out, cycle-
by-cycle current limit, and thermal shutdown.