Stereo audio subsystem offers 3-D sound for your phone

Santa Clara, CA — November 19, 2003 — National Semiconductor Corporation today introduced a Boomer audio subsystem for cell phones that integrates amplifiers, volume and mixing controls and 3D sound in a miniature micro SMD package.

National's LM4857 integrates stereo speaker drivers for the handset with 495mW output power per channel, a 33mW stereo headphone driver with 32-step volume control and independent left, right and mono volume controls. Operating on a 3.3V supply, it combines a stereo speaker amplifier for improved sound quality over single mono speakers, a mono earpiece amplifier that delivers 43mW into a 32ohm load, and a line output for an externally powered hands-free speaker (such as a car kit).

The LM4857's 3D enhancement improves stereo channel separation when the left and right speakers are too close together and solves problems that would otherwise arise from system size constraints or equipment limitations. In addition, the LM4857 routes and mixes the stereo and mono inputs into 16 distinct output modes that give designers flexibility to route and mix mono and stereo audio signals without limiting routing just to stereo speakers or stereo headphones. The LM4857 is controlled through an I2 C compatible interface.

The LM4857 is available now 30-bump micro SMD packaging and is priced at $2.70 in 1,000-unit quantities.

National Semiconductor Tel: 800-272-9959

LM4857 Product Folder

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