An integrated low-voltage SLIC/codec for short loop applications

A single chip solution for doing analog and digital signal processing for subscriber line telephony is proposed. Conventional line cards use a set of two chips for doing the same job: a low voltage mixed signal chip operating as a voice coder and a high voltage chip to fulfill high voltage requirement (up to 70 V) of the line. The proposed architecture utilizes a single chip designed in the ordinary CMOS technology to control a set of six off-chip bipolar transistors. Therefore all analog signal conditioning and line supervision is performed in the low-voltage integrated part. Simulation results show the imperfections of the low-cost bipolar transistors have minor effect on the performance relaxing the type of the bipolar transistors operating in the high-voltage front end The integration of the SLIC and codec not only saves the cost and area but also helps to do the hybrid operation (self-echo cancellation) as an integrated part of the whole line card.