New approach to a digitally programmable analogue VLSI cochlea prosthesis and its implementation with SI technique

A novel approach to the design of hearing aids system is shown. It is based on the use of switched current circuit to design analogue programmable filter. The idea consists of using the possibility to control SI circuit parameter by varying switching frequency. Indeed, SI circuits are designed using digital CMOS process since it uses only transistors to perform basic processing blocks. Our effort was focused on the design of a digitally controlling circuit in CMOS technology. We proposed a prosthesis system based on a set of audio SI filters distributed on the 8 kHz audio band. Each filter parameters are controlled by a digitally programmable PLL based frequency synthesizer and a switched weighted gain stages. The whole system is designed using only CMOS process.