An analog interface circuit (AIC) for high-speed modems

An analog interface circuit (AIC) is described that can be used with a digital signal-processing element to implement high-speed (up to 14-kHz) modems. It includes receive/transmit functions, an auxiliary DAC (digital-to-analog converter), audio monitoring, call progress tone detection, loopbacks, and a hybrid function. The chip is fabricated using a 3- mu m double-polysilicon CMOS n-well process. It is housed in a 28-pin package and the die size measures 225 mils*238 mils. It uses +or-5.0+or-0.5 V power supply and consumes 150 mW of power at 10 V. The transmit and receive filters have a PSRR (power supply rejection ratio) of 35 dB at 1 kHz and the idle channel noise (measured by grounding the filter input) of 10 dBrnCo.<>