An analog front end for combined high speed data and facsimile group 3 modems

A single-chip analog front end (AFE) for combined 9600-b/s ping-pong and facsimile group 3 dial-up modems (up to 14400 b/s) has been implemented. The AFE supports V.17/V.29/V.27 ter transmission modes for facsimile and V.32 9600/4800-b/s ping-pong for data, as well as lower speed modem full-duplex fallback modes from V.22 bis 2400 b/s down to 300 b/s. It meets all domestic and international requirements while maintaining better than 30-dB worst-case signal-to-noise ratio across the full received signal dynamic range of 48 dB. This mixed switched-capacitor/digital IC integrates 97 stages of analog signal filtering/processing with A/D and D/A converters and 1700 gates of DSP and microprocessor bus interface logic. It occupies 74000 mil² in a standard 3-μm double-poly CMOS process