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National Semiconductor Introduces Complete Boomer 3D Stereo Audio Subsystem in Miniature Package

LM4844 Integrates Output Capacitor-less Technology to Deliver High-Quality Music to Mobile Phones

Sep 12, 2005

September 12, 2005 - National Semiconductor Corporation (NYSE:NSM) today introduced the Boomer® LM4844 audio subsystem to simplify development of superior full-bandwidth stereo and 3D sound in mobile phones and other battery-powered devices. Boomer audio power amplifiers provide high-quality output power with a minimal number of external components.

“As consumers demand sophisticated features such as music playback, mobile phone manufacturers require a much higher-quality audio solution than previous phones that just carried voice content,” said Mike Polacek, vice president of National’s Audio Products Group. “Boomer audio subsystems with output capacitor-less technology, such as the LM4844, allow designers to easily implement high-quality, feature-rich audio in their phones with a minimum amount of design work and board space.”

The LM4844 integrates 1.2W stereo speaker amplifiers and headphone drivers, volume control, mixing, power management features and National’s 3D sound enhancement.  Ten pre-programmed output modes combine these features into one simple-to-use, 2.5 mm by 3 mm micro SMD package.

The LM4844’s output capacitor-less (OCL) headphone topology eliminates the need for external capacitors at the headphone outputs, saving board space. The OCL headphone topology also improves low frequency response and reduces the “pop and click” noise of the headphone amplifier. The subsystem further reduces pop and click noise from the headphone and speaker outputs through National’s suppression circuitry.

Key Technical Features
Operating on a 3.3V supply, National’s LM4844 integrated stereo speaker drivers deliver 495 mW of output power per channel into an 8-Ohm load, and the stereo headphone drivers deliver up 33 mW into a 32-Ohm load.  The subsystem is controlled through an I2C compatible interface that allows designers to utilize independent left-, right- and mono-volume controls. 

The LM4844’s 3D enhancement improves stereo channel separation when the left and right speakers are too close together and solves problems that would otherwise arise from system size constraints or equipment limitations.  In addition, the LM4844 routes and mixes the stereo and mono inputs into 10 distinct output modes which give designers flexibility to route and mix audio signals to either the stereo speakers or stereo headphones.  In addition, it features low shutdown current of 0.1 µA typical.

About National’s Audio Portfolio
National Semiconductor works with every major handset maker in the world and is the leading provider of audio amplifier systems for the cell phone market.  The company’s line of Boomer audio amplifiers enhances and enriches the entire range of sound – from voice, ring sounds and music – that can be amplified in a mobile phone.  National manufactures Class AB and Class D mono and stereo speaker amplifiers, mono and stereo headphone amplifiers, and audio subsystems for desktop and notebook computers, multimedia displays and portable electronic devices.  The company also offers its higher-power Overture® amplifiers for consumer stereo and home theater systems.  For more information on National’s audio products, visit audio.national.com.

Pricing and Availability
Available now in a 30-bump micro SMD package that measures 2.5 mm by 3 mm, the LM4844 is priced at $2 each in 1,000-unit quantities. More information on the LM4844 is available at http://www.national.com/pf/LM/LM4844.html. A large selection of audio amplifiers is supported by National’s WEBENCH® online design tool.  To explore these solutions, visit http://webench.national.com
.  To learn about high-performance audio amplifiers for portable applications, visit National’s library of online seminars

Note to editors:  To view a high-resolution downloadable photo of this product, visit National's photo gallery.

About National Semiconductor
National Semiconductor, the industry's premier analog company, creates high-value analog devices and subsystems.  National's leading-edge products include power management circuits, display drivers, audio and operational amplifiers, communication interface products and data conversion solutions. National's key analog markets include wireless handsets, displays and a variety of broad electronics markets, including medical, automotive, industrial, and test and measurement applications. Headquartered in Santa Clara, California, National reported sales of $1.91 billion for fiscal 2005, which ended May 29, 2005.  Additional company and product information is available at www.national.com
.