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National Semiconductor Introduces Industry’s Smallest Audio Subsystem with Class D Speaker Driver

LM4935 Integration in New Micro SMDxt Package Saves Up to 70 Percent Board Space

Jan 9, 2006

January 9, 2006 - The industry’s smallest audio subsystem with a mono Class D speaker driver from National Semiconductor Corporation (NYSE:NSM) integrates all the analog and digital audio functions needed for smart phones and voice-over-Internet protocol (VoIP) phones. In a related announcement today, National released additional details of the subsystem’s new 4 mm by 4 mm micro SMDxt package, which saves up to 70 percent board space over existing packages. A member of the Boomer® audio power amplifier family, the LM4935 subsystem provides high-quality output power with a minimal number of external components.

“Smart phones bring the convergence of PDA functionality, wireless connectivity and, increasingly, consumer audio to one full-featured device,” said Mike Polacek, vice president of National’s Audio Products Group. “The LM4935 allows handset designers to add the new audio features consumers demand.  Its integration drives design simplicity and takes up a minimum amount of board space.” 

Key Technical Features and Benefits
The LM4935 is a complete audio subsystem with multiple digital and analog inputs and outputs. Operating on supplies ranging from 1.8V to 5.5V, the LM4935 combines several features: a Class D speaker amplifier delivering 570 mW into an 8-Ohm load; a stereo headphone amplifier that supports output capacitor-less (OCL) or AC-coupled operation delivering 30 mW per channel into a 32-Ohm; a mono earpiece amplifier delivering 30 mW into a 32-Ohm load; and a line output for an external-powered handsfree speaker providing filter-less Class D stereo speaker capability. Other features include a successive approximation register (SAR) analog-to-digital converter (ADC) for system monitoring and a high-fidelity digital-to-analog converter.

The LM4935’s bi-directional I2S digital interface with pulse-code modulation (PCM) capability transmits any audio file or voice data transmission back and forth from the baseband application-specific integrated circuit (ASIC) or processor to the analog outputs. The subsystem also features a read/write I2C compatible digital interface. 

In addition, the LM4935 gives engineers design flexibility in arranging analog inputs through a sophisticated switching/mixing circuitry, eliminating the need for external audio switches and mixing components. Two analog inputs allow the LM4935 to accept a stereo signal from an FM radio or operate as two separate mono inputs that can accept other analog input signals. Additional analog inputs allow for differential mono input and output from a GSM, CDMA or other cell phone radio module as well as a baseband application-specific integrated circuit (ASIC).  Two additional inputs support internal and external microphone capability.  

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
Available now in a 49-bump micro SMDxt package, the LM4935 is priced at $3.95 each in 1,000-unit quantities. More information and easy-to-order samples are available at http://www.national.com/pf/LM/LM4935.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 and headphone amplifiers, 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.