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Optoelectronics/Displays??

LMUs drive up to 20 series-connected LEDs

Posted: 29 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:National Semiconductor? lighting management units? LMU? LP3958? LP5526?

National Semiconductor Corp. introduced two new, highly integrated lighting management units (LMUs) that include a high-voltage boost converter and programmable constant-current driver to control up to 20 series-connected LEDs in display backlights, and keypad, RGB and camera flash LEDs. The LP3958 and LP5526 LMUs feature tiny micro SMD packages and are well-suited for cellphones and other handheld devices.

According to the company, the new LMUs drive from two to five strings of four series-connected LEDs, depending on the lighting application. They are optimized for use in single- or dual-display phones, as well as large display PDA phones. Each features three GPIOs to trigger lighting functions such as flash or to control additional device-enable signals. The LP3958 features 70mA of output current for powering display backlight LEDs and the LP5526 features 150mA of output current for powering display backlight and Flash LEDs. Both devices include an I2C interface.

The GPIO functions enable the user to control external devices. The serial interface reduces the wire count through the hinge in flip cell phone designs. For keypads, three series-connected LED strings of up to four LEDs each can be independently controlled to enable light segmentation. This is particularly useful in gaming and navigation applications, for example, in which individual buttons can be selected for illumination.

In single and dual displays, the LP3958 LMU drives up to eight white LEDs grouped as four series-connected LEDs per string, with typically one string per display. Display backlight fade in and fade out is controlled via a two-wire, low-voltage, I2C-compatible interface, allowing easy software implementation.

The LP5526 can drive multi-die serial-flash LEDs in camera flash (up to 3W of power) and torch applications. Also, in the case of a software problem, it features an internal safety timer to protect Flash LEDs from aging. LP5526's Flash LED output can also be used to drive single or series-connected RGB LEDs.

Available in 2.5-by-2.5mm, 25-bump micro SMD packages, the LP3958 and LP5526 devices are priced at $1.60 and $2, respectively, in 1,000-unit quantities.




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Related Datasheets
Part Number Description Category
? LP5526 Lighting Management Unit with High Voltage Boost Converter with up to 150mA Serial FLASH LED Driver from the PowerWise? Family ICs, Interface

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