Battery supplied low power analog-digital front-end for audio applications

This paper presents the development of a full custom low power, mixed-mode, analog digital front-end chip for audio applications. The front-end is used with a full custom DSP ASIC in a high performance hearing aid system. The front-end implements functions as preamps, low power stereo audio analog to digital converters, remote-control receiver, high PSSR power supplies, time base, voltage reference and a DC-DC converter. The chip has around 170K MOS and is operating down to 0.9V from the battery. The chip is produced using a 0.35 µm, 3.3V CMOS process with quadruple metal, two poly resistors and double poly capacitors.