SGS-THOMSON is first to market with multimedia analog front end chip for two-chip PC Audio and communication architecture

October 7, 1996 SGS-THOMSON Microelectronics today announced the availability of a multimedia analog front end integrated circuit that allows PC designers to implement immediately a powerful two-chip unified audio architecture comparable to the recent "AC97" proposal.

Called STLC7549, the chip integrates all of the analog functions for an advanced multimedia personal computer, including CD-quality audio, telephony and V.34bis Digital Simultaneous Voice and Data (DSVD) modem in a 64-pin TQFP package. This reduces power consumption, size and board complexity.

Most personal computers shipped today include sound capability plus a modem for fax, data and telephony. All of these functions require an analog front end plus audio interfaces for speakers, microphones and the phone line; complex digital processing is also needed for these functions. To address this need, several companies have recently published a proposed specification for an audio and communication architecture called AC97. This architecture defines a two-chip system with a digital processor and an analog circuit.

While the AC97 specifications were being published SGS-THOMSON was already fabricating the first wafers of the STLC7549 chip which, though it was developed independently, offers the features required by AC97, and more besides. A comparison between the requirements of AC97 and the functions of the STLC7549 is attached.

"The endorsement of our architecture choices by the AC97 proposal underlines that SGS-THOMSON is the real leader in analog CODEC technology, delivering silicon while others are still publishing proposals", commented SGS-THOMSON's Bruno Defretin, manager of SGS-THOMSON's Telecom Terminals Business Unit. "The fact that the STLC7549 offers greater functionality than required by AC97 only serves to further reinforce our position."

With a 16-bit sigma-delta architecture, the STLC7549 offers outstanding performance. Dynamic range exceeds 90dB for the modem section and 85dB for the audio part, with a sampling frequency programmable up to 48kHz.

Inside the chip, the audio section includes full duplex stereo channels that allow independent output mixing and recording mixing of multiple inputs, each of which can be amplified, attenuated or muted independently. The telephony section provides mono mixing of two mono inputs from a second phone line and a headset and three mono outputs for the phone speaker, headset speakers, second line modem, fax or rear game channel. The modem section includes a differential mono input and output line for the V.34bis standard. The telephony and modem parts are independent of the audio section thanks to a second sampling clock and serial port. However, all clocks can also be controlled from a master clock providing a quadrophonic mode for surround sound and 3D sound applications.

To speed development of STLC7549 applications SGS-THOMSON offers a support package consisting of two boards and Windows based PC software that controls all of the chip functions through an interactive interface with mixers and volume controls. Every STLC7549 internal register can be monitored at all times with its datasheet information displayed on-screen. One board is the STLC7549 Application Board and contains the chip itself plus the audio connectors, phone line interfaces and so on. The second board is the STLC7549 Control Board and contains an ST9 microcontroller, memory, logic and the PC interface. Initially developers will work with both boards and a PC so that work can begin immediately. Later the Control Board can be replaced by the digital section of the system being designed. The PC software can also work without the boards in a standalone mode that allows simulation of the STLC7549.

The STLC7549 is the latest fruit of knowhow gathered by SGS- THOMSON in many years of activity in analog front end chips for modems and cellular telephones, a field in which the company is a recognized leader.

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