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National Semiconductor has introduced a small white light-emitting-diode (LED) driver with dynamic display backlight control.

The LM3530, a member of the company’s Powerwise energy-efficient product family, drives up to 11 high-current LEDs in series, illuminating larger displays in portable media devices such as smartphones.

The driver is offered in a 12-bump micro SMD package measuring 1.615mm x 1.215mm x 0.425mm.

According to the company, today’s increased multimedia content in portable devices is fuelling the trend towards larger displays and longer video playback, which require more power.

National Semiconductor’s LM3530 LED driver employs ambient light-sensing algorithms and content-adjustable backlighting to optimise the display, realising up to a 55 per cent power saving over the common practice of driving the backlight at a constant brightness.

In a pair of tests, the company compared the energy consumption of a backlight illuminating a 3.5in (8.9cm) Ipod touch display with and without the 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 movie.

Results showed the LM3530 achieved a power saving of 43 per cent and 55 per cent 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.

The LM3530 current-mode boost converter can supply up to 29.5mA 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 and brightness and image performance.

The LM3530’s programmable ambient light response, along with a separate pulse-width modulation (PWM) dimming input, enables the backlight LED driver to determine lighting requirements and select between various dimming options, optimising the light output for the given conditions.

Logarithm and linear LED brightness mapping provides flicker-free dimming.

A fixed-frequency 500kHz 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 Semiconductor is planning to offer a product with a similar feature set in October 2009.

Available now, the LM3530 is priced at USD1.99 (GBP1.21) in 1,000-unit quantities.

National Semiconductor

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