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National Semiconductor’s New Boomer Stereo Class D Audio Subsystem Provides 3D Enhancement, Headphone Detection

Integrated Filterless 2.2W Amplifier Offers Flexible I2C Compatible Controls

Jan 11, 2007

January 11, 2007 – National Semiconductor Corporation today introduced a Boomer® audio subsystem that combines a 2.2W stereo Class D audio amplifier with National’s programmable 3D sound enhancement, automatic headphone detection and a 155 mW, stereo output capacitor-less (OCL) headphone amplifier. The subsystem is well-suited for portable media players, portable DVD players and multimedia cell phones.

National’s fully integrated LM49270 filterless subsystem with high output power provides a flexible I2C compatible serial interface to quickly adjust the integrated circuit for multiple application requirements. Its headphone detection feature allows the subsystem to automatically switch between speaker and headphone mode. The LM49270’s stereo headphone amplifier can be configured as either a capacitive-coupled or OCL device for more design options. With the OCL architecture, designers can eliminate the bulky, expensive output coupling capacitors required by traditional headphone amplifiers.

The subsystem also provides a wide, 32-step volume control for the headphone and speaker output levels. The LM49270 has 4.7 mA quiescent power in headphone mode to extend the battery life and delivers 2.2W of output power into a 4-Ohm load with less than 10 percent total harmonic distortion plus noise (THD+N) for a 5V supply. 

Additional Key Features and Benefits

  • Headphone sense circuitry detects the presence of a headphone and configures the device accordingly  
  • Multiple mode selection and volume levels through on-chip I2C compatible interface  
  • Independent speaker and headphone volume controls  
  • Output short-circuit and thermal overload protection  
  • Click and pop suppression  
  • Micro-power shutdown

Pricing and Availability
The LM49270, offered in a 28-pin LLP® package, is priced at $2.45 each in 1,000-unit quantities. More information and easy-to-order samples are available at http://www.national.com/pf/LM/LM49270.html. To learn about high-performance audio amplifiers for portable applications, visit National’s library of online seminars.

About National’s Audio Portfolio
National Semiconductor has been a leading provider of audio solutions for more than 30 years and offers a wide range of products in its Boomer®, Overture® and high-performance audio lines. National works with every major handset maker in the world and is the leading provider of analog audio solutions for the cell phone market. The company's line of Boomer audio amplifiers and subsystems enhance and enrich the entire range of sound – from voice, ring sounds and music – that can be amplified in mobile phones and other portable equipment.  National manufactures Class AB and Class D speaker amplifiers, headphone amplifiers and audio subsystems for many applications ranging from portable devices to high-power, high-fidelity audio systems. The company offers its higher-power Overture amplifiers for mid-performance consumer applications, and National’s new high-performance series brings dramatically improved sound quality to high-fidelity consumer and professional audio equipment. 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, 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, Calif., National reported sales of $2.16 billion for fiscal 2006, which ended May 28, 2006.  Additional company and product information is available at www.national.com.