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National Semiconductor Offers Next-Generation Boomer Audio Amplifiers For Driving Ceramic Speakers in Portable Applications

Industry’s Smallest Ceramic Speaker Drivers Enable Credit-Card-Thin Handsets

Jan 23, 2006

January 23, 2006 - National Semiconductor Corporation (NYSE:NSM) today introduced two single-chip Boomer® audio power amplifiers in ultra-small packages. The LM4962 and LM4953, the next generation in National’s industry-leading ceramic speaker driver family, provide high capacitive loads for portable applications such as cell phones, smartphones, notebook computers and other small handheld devices.

"National is the leader in ceramic speaker driver technology for portable devices,” said Mike Polacek, vice president of National Semiconductor’s Audio group. "The LM4962 and LM4953 integrated drivers allow manufacturers to create credit-card-thin handsets or add additional features to designs because the chips save space and reduce power consumption. This enables longer battery life and talk time."

Ceramic speakers are dramatically different from conventional moving coil speakers.  They act as a capacitive load rather than a resistive load and require much more voltage, but less current.  Compared to traditional moving coil speakers, which are 4 mm or more in thickness, ceramic speakers are only 0.7 mm thick and often weigh less than one gram.  More information on these speaker types is available in National’s Audio Education Series eBooks at audio.national.com.

The LM4962 ceramic speaker driver saves designers 80 percent board space over National’s previous generation, reducing the integrated circuit size from 25 square mm to 5 square mm. To address the high voltage needs of ceramic speaker’s capacitive loads, the chip integrates a boost converter with an audio power amplifier for mono ceramic speaker applications. For stereo applications, the boost converter of the LM4962 also can drive a second external audio high-voltage amplifier such as National’s LM4951.

The LM4953 ceramic speaker driver is National’s first audio amplifier to use a charge pump to drive the ceramic speakers. The LM4953 requires only eight external components, saving board space and replacing the need for an expensive voltage regulator and large inductor.

High Performance, Low Power
The LM4962 ceramic speaker driver provides 15V peak to peak across a bridge-tied-load (BTL) with less than 1 percent total harmonic distortion plus noise (THD+N) from a 3.2V DC power supply. In addition, the LM4962 features overcurrent protection for the boost converter and overvoltage protection. The DC/DC converter features a soft-start function.  The LM4962 includes added battery savings, with a low-power mode for earpieces and a high-power mode to drive the ringtones and handsfree speakers. 

The LM4953’s audio amplifier and integrated charge pump, in a 3 mm by 4 mm package, allow a voltage boost from a 3.6V supply, delivering 12.6V peak-to-peak across a 2uF + 30-Ohm BTL with less than 1 percent (THD+N). 

These speaker drivers feature a low-power consumption shutdown mode and an internal thermal shutdown protection mechanism. They do not require bootstrap capacitors or snubber circuits. In addition, they contain advanced “pop and click” circuitry to eliminate noises that typically occur during turn-on and turn-off transitions. Both are unity-gain stable and can be configured by external gain-setting resistors.

Pricing and Availability
The LM4962, available in a 20-bump thin micro SMD package, is priced at $2.50. The LM4953 is priced at $1.85 in a 14-pin pullback LLP® package.  The LM4951 is offered in both LLP and micro SMD packages. All prices are in 1,000-unit quantities. These chips are offered in standard or lead-free packages.

More information, as well as easy-to-order samples and evaluation boards, is available at http://www.national.com/pf/LM/LM4951.html
, http://www.national.com/pf/LM/LM4953.html and http://www.national.com/pf/LM/LM4962.html.  A large selection of audio amplifiers is supported by National’s WEBENCH® online design tool at 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 these products, visit National's photo gallery at http://www.national.com/company/pressroom/gallery/audio.html.

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
http://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
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