An 0.8-mu m CMOS mixed analog-digital integrated audiometric system

This paper presents a dual-channel fully integrated audiometric system, whi ch generates the complete set of audio and control signals required for exh austive audiometric tests. The system includes a novel signal generator, ba sed on the direct digital synthesis technique, which fulfills the requireme nts of advanced audiometric tests. The proposed system faces two different problems, namely, the generation of a finely tunable pure sinewave and the generation of noise signals with a controlled spectrum. To achieve tuning c apabilities down to 1 Hz at 20 kHz and 15 mu Hz at 100 Hz, a fractional div ision of a 40-MHz master clock based on noise-shaping techniques is perform ed. Moreover, for noise generation, a novel circuit based on pseudorandom s equences combined with analog sn itched-capacitor filters is used, The chip is fabricated in a 0.8-mu m CMOS process and occupies a 24.2-mm(2) silicon area. It consumes 45 mW from a single 5-V power supply and achieves less t han -90-dB crosstalk between the channels.