National Semi rolls LED driver with online design environment

Santa Clara, Calif. — National Semiconductor Corp. has introduced a high-brightness LED driver with temperature management control and the addition of an online design environment to support it. The LM3424, a member of National’s PowerWise energy-efficient product family, drives high-brightness LEDs in a variety of indoor, outdoor and automotive applications.

Supported in National’s WEBENCH LED Designer, its temperature management control, thermal foldback, enables lighting designers to easily design a reliable thermal system using the LM3424. Thermal foldback deals with high temperatures LEDs can reach as a result of environmental conditions. When LED temperatures rise above a safe threshold, the lifetime and efficacy of the LED decreases, said National. With the LM3424, lighting designers can program temperature and slope breakpoints in order to safely operate the LEDs.

When an over-temperature condition occurs, the LM3424’s thermal foldback circuitry reduces the regulated current through the LEDs. The reduced current dims the LED to a range programmed by the designer and the LED remains within the range until it returns to a safe operating temperature, said National.

This method of thermal foldback maintains the lifetime and efficacy of the LED and ensures the warranty period of fixtures in applications such as automotive headlights, high bay warehouse lighting and street lighting, said National.

The WEBENCH online design environment allows the designer to enter the temperature foldback and slope points and then visualize the behavior of the design at different LED temperatures without hand calculations. An interactive temperature slider shows the results graphically. The LED driver design automatically updates with entry of temperature breakpoint requirements.

Offered in a 20-pin thermally enhanced TSSOP package, the LM3424 drives up to 18 high-brightness LEDs in series with output current above 2A in a typical application. It contains all of the features to regulate currents based on buck, boost, SEPIC, flyback and buck-boost topologies.

The LM3424 operates over a wide input range of 4.5V to 75V. The pulse-width modulation (PWM) controller is designed for high-speed capability including an oscillator frequency range that can be synchronized up to 2.0 MHz. Other features include PWM and analog dimming, programmable softstart and protection features such as low-power and thermal shutdown, and cycle-by-cycle current limit.

Pricing: Available now, the LM3424 is priced at $1.75 in quantities of 1,000.
Resources: LED drivers.