NSC cellphone audio subsystem offers 3D sound

National Semiconductor Corp. (NSC) has introduced a Boomer audio subsystem for cellphones that integrates amplifiers, volume and mixing controls and 3D sound in a miniature micro SMD package. The 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, the product combines a stereo speaker amplifier for improved sound quality over single mono speakers, a mono earpiece amplifier that delivers 43mW into a 32-ohm load, and a line output for an externally powered hands-free speaker.

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. It is controlled through an I?C compatible interface.

Available in a 30-bump micro SMD packaging, the device is priced at $2.70 for 1,000-unit quantities.