An analog telephone subscriber chipset integrating 16 lines with fully programmable central office impedance

This paper describes the chipset (3 ASIC's) for an analog telephone subscriber line circuit: a 16 channel digital circuit performing speech band filtering, echo cancellation, A-law//spl mu/-law coding and controlling interface, an 8 channel analog/digital circuit performing the A/D and D/A conversion with analog filtering, and an analog high voltage BICMOS circuit covering the SLIC (Subscriber Line Interface Circuit) function with special attention for the integration of software programmable synthesized AC and DC impedances.