LT3519-1 is a fixed frequency step-up DC/DC converter designed to drive LEDs. It feature an internal 45V, 750mA low side switch and Schottky diode. Combining a traditional voltage feedback and a unique rail-to-rail current sense feedback allows this converter to operate as a constant-voltage source or constant-current source. Internal compensation simplifies applications. This device feature rail-to-rail LED current sense pins that provide the most flexibility in choosing a converter configuration to drive the LEDs. The LED current is externally programmable with a sense resistor. The external PWM provides up to 3000:1 PWM dimming and the CTRL input provides analog dimming. It is widely used in application such as automotive, industrial, constant current source, current limited constant voltage source etc.