National Semiconductor Introduces New White LED Driver LM3530

National Semiconductor Corporation (NS) has announced the industry's smallest white LED driver with flexible control of display backlight brightness. The LM3530 boost converter is a National Semiconductor PowerWise energy-efficient chip family that can drive up to 11 high-current LEDs in series to provide adequate backlighting for large displays in portable multimedia electronics such as smartphones. The LM3530 is packaged in a 12-bump micro SMD package. The entire chip is only 1.615mm × 1.215mm × 0.425mm.

As the multimedia content played by portable electronic products is becoming more and more colorful, the display screens are getting larger and larger, and the time for playing the short films is getting longer and longer. Accordingly, this also causes a problem of a large increase in power consumption. National's LM3530 LED driver uses advanced ambient light detection algorithms and adjusts backlight brightness based on video content. Compared to common backlight systems with constant brightness, the LM3530's system is not only clear and bright, but also saves up to 50% in power consumption.

National Semiconductor has tested the power consumption of the backlight system of the 3.5-inch iPod touch display. The tests were divided into two groups, one of which used National's LM3530 LED driver, while the control group did not.

The video content for testing is some common multimedia video material downloaded from the Internet, such as one episode of a TV series and a trailer for a movie. Test results show that the backlight system using the LM3530 chip consumes less power, and its actual power consumption is reduced by 43% and 55%, respectively, compared to the conventional backlight system. Since the movie trailer has more dark images and less backlighting, the energy saving effect is more obvious.

Technical specifications

National's LM3530 current-mode boost converter can use up to 29.5mA of drive current for 11 white LEDs with a single lithium battery. System designers can use the I2C-compatible interface to set up a variety of light effects such as fade out, external environment and lighting levels, and brightness and image effects.

The LM3530 also has an ambient light response time and a separate PWM dimming input. Therefore, this LED backlight driver can flexibly determine the required backlight brightness according to the actual environment, and then choose among different dimming schemes to provide the most suitable light output for different practical environments. The chip uses a logarithmic function and linear LED brightness mapping technology to ensure that there is no flicker when dimming. The LM3530 boost converter uses a fixed 500kHz frequency, so the efficiency can be kept at an extremely high level as long as the LED current does not exceed its specified range.

A large-screen display backlight system with a series LED configuration can reduce system power consumption by using the LM3530 chip as a driver. For displays with parallel charge pumps, National Semiconductor will launch another product with similar features in October 2009.

Price and availability

National's LM3530 chip is priced at $1.99 in 1,000-unit quantities and is available in volume.

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