National Semiconductor - White LED Driver with Dynamic Backlight Control Reduces Power Consumption of Portable Displays up to 55 Percent

Today’s increased multimedia content in portable devices is fueling the trend towards larger displays and longer video playback, which require more power. National’s LM3530 LED driver employs sophisticated ambient light-sensing algorithms and content-adjustable backlighting to optimize the display, realizing up to a 55 percent power saving over the common practice of driving the backlight at a constant brightness.

In a pair of tests, National compared the energy consumption of a backlight illuminating a 3.5” iPod touch display with and without National’s LM3530 LED driver.

The evaluation was conducted using typical multimedia downloadable material, in this case an episode from a television series and a trailer from a popular movie. Results showed the LM3530 achieved a power savings of 43 percent and 55 percent, respectively, over traditional backlighting. The predominately darker picture in the movie trailer garnered further power savings because the backlight was reduced more frequently for dark images.

National’s LM3530 current-mode boost converter can supply up to 29.5 mA of power to 11 white LEDs from a single-cell Lithium-Ion battery. A wide degree of programmability via an I2C compatible interface enables the designer to adjust for lighting effects such as fading, external ambient conditions and lighting level, as well as brightness and image performance.


The LM3530’s programmable ambient light response along with a separate pulse-width modulation (PWM) dimming input enable the backlight LED driver to intelligently determine lighting requirements and select between various dimming options, optimizing the light output for the given conditions. Logarithm and linear LED brightness mapping provides flicker-free dimming. A fixed-frequency, 500 kHz boost converter provides high efficiency over the LED current range.


The LM3530 brings power savings to the serial implementation of large display backlighting. For parallel charge pumps, National will offer a product with a similar feature set in October 2009.
Available now, National’s LM3530 is priced at $1.99 in 1,000-unit quantities. More information about National’s LED drivers is available at http://www.national.com/led.