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National Semiconductor Introduces Industry’s First Stereo Audio Subsystem With Both Digital and Analog Inputs

LM4934 Offers 3D Enhancement for Improved Stereo Audio Sound in New Package with Small Footprint

Dec 12, 2005

December 12, 2005 - National Semiconductor Corporation today introduced the LM4934 Boomer® stereo audio subsystem, the industry’s first subsystem to incorporate both digital and analog input paths for multimedia, smart and voice-over-Internet procotol (VoIP) phones. National’s Boomer audio power amplifiers provide high-quality output power with a minimal number of external components.

“Cell phone manufacturers use a combination of digital and analog sources in their designs,” said Mike Polacek, vice president of National Semiconductor’s Audio group. “For example, the output of an MP3 decoder may be digital, while an FM radio module’s output may be analog. This flexibility, combined with the on-chip features, helps engineers save components, board space, cost and design time.”

The LM4934 audio subsystem integrates audio amplifiers, volume control, a mixer, power management control and National’s 3D stereo sound-enhancement technology into a new, 3.3 mm by 3.9 mm, 42-bump micro SMDxt package. The 3D capability makes it easier for listeners to hear music more clearly through the phone by broadening the sound field of the closely placed speakers.

Key Technical Features and Benefits
The LM4934 offers an I2S digital input and three analog inputs, which eliminate the need for an external digital-to-analog converter (DAC) and a multiplexer integrated circuit. Operating on a 3.3V supply, the single-chip LM4934 combines a stereo speaker amplifier delivering 500 mW typical per channel into an 8-Ohm load and a stereo headphone amplifier delivering 30 mW typical per channel into a 32-Ohm load. The chip features a 25 mW mono earpiece output and a separate line out to drive external audio devices.

The on-board phased-lock loop (PLL) simplifies the customer’s selection of a clock frequency (from 8 MHz to 24 MHz) and saves cost by eliminating the need for an external crystal oscillator. The entire chip is controlled through 25 separate I2C compatible registers for maximum flexibility of routing inputs and outputs through the two-wire interface.  In addition, the LM4934 routes and mixes the stereo and mono inputs into multiple, distinct output modes using a simple I2C compatible interface.

Innovative, Advanced Packaging
National’s new micro SMDxt package provides high input/output analog devices with the smallest possible footprint for any given pin count. The micro SMDxt, which builds on the success of National’s micro SMD package, utilizes a unique solder ball structure that enables high-reliability products with bump counts up to 100 bumps at a 0.5 mm pitch. With the new package, reliability requirements for typical portable applications such as thermal cycling, thermal shock, drop test and flex test can be met without the use of an underfill.

National produces billions of chips per year and packages them in more than 70 different package types.  The company has more than 290 patents in package technologies and receives approximately 30 new packaging patents each year. National has introduced several packaging innovations to the industry, including both the micro SMD and LLP® packaging technologies.

Pricing and Availability
The LM4934, available now in a standard 42-bump micro SMDxt package, is priced at $3.80 in 1,000-unit quantities. A lead-free package will be available in early 2006. More information on this product is available at http://www.national.com/pf/LM/LM4934.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’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 and headphones, as well as 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.

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.