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Boomer audio amp incorporates digital, analog input paths

Posted: 19 Dec 2005 ?? ?Print Version ?Bookmark and Share

Keywords:National Semiconductor? LM4934? Boomer stereo audio amplifier?

National Semiconductor Corp. introduced the LM4934 Boomer stereo audio subsystem, which it touts as the industry's first subsystem to incorporate both digital and analog input paths for multimedia, smart and voice-over-Internet procotol (VoIP) phones.

"Cellphone manufacturers use a combination of digital and analog sources in their designs," said Mike Polacek, VP of National'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 new LM4934 audio subsystem integrates audio amplifiers, volume control, a mixer, power management control and National's 3D stereo sound-enhancement technology into a 3.3-by-3.9mm, 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, added the company.

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

The on-board phased-lock loop simplifies the customer's selection of a clock frequency from 8MHz to 24MHz, 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.

The LM4934 is available in a standard 42-bump micro SMDxt package, and priced at $3.80 in 1,000-unit quantities. A Pb-free package will be available in early 2006.

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Related Datasheets
Part Number Description Category
? LM4934 3D Audio Sub-System with Stereo Speaker, OCL/SE Stereo Headphone, Earpiece and Mono Line Level Outputs Passives - Filters, Oscillators and Resonators



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