By Texas Instruments 31
National Semiconductor's LM3407 is a constant current output floating buck switching converter designed to provide constant current to high power LEDs. The device is ideal for automotive, industrial and general lighting applications. The LM3407 has an integrated power N-MOSFET that makes the application solution compact and simple to implement. An external 1% thick-film resistor allows the converters output voltage to adjust as needed to deliver constant current within 10% accuracy, to a serially connected LED string of varying number and type. Converter switching frequency is adjustable from 300 kHz to 1 MHz. The LM3407 features a dimming input to enable LED brightness control by Pulse Width Modulation (PWM). Additionally, a separate enable pin allows for low power shutdown.