LED driver with dynamic headroom control suits high-power applications

National Semiconductor Corp. announces an LED driver with dynamic headroom control and multiple outputs for high-power applications that accurately and efficiently drives up to four strings of LEDs. The LM3464, a member of National’s PowerWise energy-efficient product family, maximizes system efficiency and reduces system complexity and cost in LED-intensive applications such as industrial, street, and automotive lighting.

Unlike traditional high-brightness LED drivers that drive current to each string independently, the LM3464 LED driver includes four channels to drive up to 20 LEDs per channel, reducing system complexity and cost. The LM3464’s dynamic headroom control feature dynamically adjusts the LED supply voltage through the power supply feedback to the lowest level required to provide optimal system efficiency.

The new driver is a high-voltage current controller with four individual current regulator channels. It works in conjunction with external N-channel MOSFETs and sense resistors to accurately drive current to each LED string. The LM3464 features a wide input voltage range up to 80 V to drive multiple LEDs per string, making the LM3464 suitable for LED-intensive applications.

A thermal foldback feature protects the LEDs from unsafe temperatures that can significantly degrade the light output or lifetime of the LEDs. During an over-temperature condition, the thermal foldback reduces the current through the LEDs until the LED junction temperature of the LEDs returns back to a safe operating temperature. This user-programmable feature allows for a more robust and reliable thermal design, helping to ensure the lifetime and light output of the LEDs over time and through temperature variances due to environmental conditions of the fixture.

The dynamic headroom control feature monitors the forward voltages of the LED strings and dynamically adjusts the LED supply voltage through the power supply feedback to the lowest level required. By directly controlling the output of the offline regulator, the LM3464 can eliminate the second stage switching regulator commonly required for offline LED power supplies.

The LM3464 features both pulse-width modulation (PWM) and analog dimming interfaces to allow the user to select between various dimming types for different applications. Protection features include VIN under-voltage lock-out, LED open/short circuit, and over-temperature fault signaling to the system controller.

For more information, contact National Semiconductor Corp., 3689 Kifer Road, Santa Clara, CA 95051. Phone: (800) 272-9959.