APPLICATION NOTE 4316

LED-Driver Design for Automotive Rear Lighting

By: Anil Baby

Abstract: For many automobiles, the same set of LEDs illuminates both tail lights and brake lights. The LEDs must therefore operate at two different brightness levels: full brightness for braking, and 10% to 25% of that brightness (dimmed) for the tail lights. Dimming is best achieved with pulse-width modulation (PWM), which maintains the LED's color spectrum over its brightness range. Moreover, an LED-driver IC that generates an internal 200Hz ramp signal can simplify the driver design by eliminating the need for an external PWM signal. This application note uses the MAX16804 high-brightness LED (HB LED) driver. The MAX16804 integrates a dual-mode DIM pin and on-board 200Hz ramp generator, eliminates the need for an external PWM signal, and simplifies the driver design.