Micro-SMD packaging provides smallest white LED drivers

Date Announced: 16 Mar 2005

National Semiconductor Corporation has introduced three new charge-pump-based white light-emitting diode (LED) drivers for mobile phone display backlighting. The LM27953, LM2796 and LM27961 white LED drivers feature a tiny chip-scale 18-pin micro SMD package that provides the smallest footprint in the industry.

These products complement National's industry-leading portfolio by providing greater flexibility for LED configurations. The LED drivers provide highly efficient LED backlighting for portable devices including digital still cameras, MP3 players, personal digital assistants, hard disk drives, wireless local area networks and other low-power, small form-factor products.

"In 2003, National Semiconductor's industry-leading white LED drivers enabled the fast adoption of color displays in mobile phones," said Peter Henry, vice president of National Semiconductor's Portable Power Products Group. "National continues to lead the market with the introduction of three more products into an already successful family of backlight drivers."

Key Technical Specifications
All three charge-pump-based white LED drivers are ideal for display backlighting and operate from an extended Li-Ion input voltage range of 2.7 V to 5.5V. The voltage boost is achieved with a high-efficiency 3/2x gain charge pump. Packaged in a tiny 18-bump micro SMD, each white LED driver features pulse-width-modulation (PWM) brightness control.

The LM27953 drives four LEDs for display backlighting or other LED lighting applications. The regulated internal current sources deliver excellent brightness matching in all LEDs by providing low-side current drivers to accommodate common-anode-type LEDs. The brightness of the LEDs can be adjusted independently with an external resistor.

The LM2796 drives up to seven LEDs in parallel with up to 20mA of current through each LED. The regulated internal current sources deliver excellent current and brightness matching in all LEDs. The LED driver current sources are divided into two independently controlled, high-side driven groups. The primary four-LED group can be used to backlight up to a 2.5-inch display, while the secondary three-LED group can be used to backlight a second display or provide other LED lighting features.

The current sources of the LM27961 are divided into two independently controlled, high-side and low-side driven groups. The primary four-LED low- side group can be used to backlight up to a 2.5-inch display, while the secondary three-LED high-side group can be used to backlight a second display or provide other LED lighting features. The brightness of the two LED groups can be adjusted independently.

Pricing and Availability
The LM27953, LM2796 and LM27961 are all available now in tiny chip-scale 18-pin micro SMD packaging. Priced in 1,000-unit quantities, the LM27953 is $1.20, the LM2796 is $1.60 and the LM27961 is $1.50. Evaluation boards are also available now.

More information about the products is available at
http://www.national.com/pf/LM/LM27953.html,
http://www.national.com/pf/LM/LM2796.html and
http://www.national.com/pf/LM/LM27961.html.

Contact
Reader Information Design Support Group (800) 272-9959

E-mail:info@iop.org

Web Site:http://www.national.com

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