Low Voltage Voice CODEC Suits Digital Cellular and Cordless Phones

Designed for digital cellular and cordless telephone applications, the SGS-THOMSON ST5090 Voice coder-decoder (CODEC) operates on 3.3V supplies and consumes only 21mW in operation and draws just 0.5uA at 3.3V in standby.

Inside the integrated circuit is a complete CODEC and filter system, including 14-bit linear analog-to-digital and digital to analog converters, 8-bit A-law or u-law companding A/D and D/A converters, transmit/receive bandpass filters and an active anti-alias noise filter..

Additionally the chip includes all of the other audio front end functions needed in a telephone terminal application: microphone selection switch and preamplifier, earpiece driver, sidetone circuit, turn on/off transient suppressor, ring tone generator and buzzer output..

Many of the device functions can be programmed by loading commands through a microwire compatible serial control channel that can be easily interfaced to standard microcontrollers. Control registers can be changed while the device is in standby state..

The microphone and earpiece circuits can be programmed to adapt to any kind of transducer. Moreover, a three-input analog multiplexer at the preamplifier input allows great flexibility in product design since the CODEC can receive audio from several sources. Transmit gain is fully programmable and can reach 42.5dB. The tone generator can be programmed to create DTMF and musical tones..

The ST5090 is suitable for cellular telephones for the European GSM, Japanese PHS and US IS-54/IS-95 standards. It also suits the CT2 and DECT digital cordless telephones. It may also be used in any battery powered equipment that needs an audio CODEC operating on single low supply voltages..

The ST5090 is now in production in 28-lead Small Outline DIP (SO-28) and 44-lead Thin Quad Flat Pack (TQFP 44) packages. A bare die version will be available later in 1996..

Also available is a complete evaluation board, driven by a PC Windows softwar via the RS232 interface. All of the programmable features can be set by simple mouse clicks on the on-screen interactive schematic diagram. (Order code is ST508X/90DEMO1).

The software is available as well free of charge in stand-alone mode to simulate the circuit..

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