A CMOS analog-digital audio processor for a portable radiotelephone

A mixed analog-digital (A/D) integrated circuit (IC) specifically designed to realize the audio processing functions needed for a portable radiotelephone (PRT) application is described. Multirate signal processing techniques are used to reduce the capacitance spread, and hence the overall silicon area, of the chip, as well as to minimize the settling requirements of the amplifiers for lower power consumption. This, together with programmable power-saving control circuitry also incorporated on-chip, considerably extends the lifetime of the battery. A semicustom design methodology is employed to implement such an application-specific integrated circuit (ASIC) in a 3- mu m CMOS double-poly processing technology. Experimental results are presented to demonstrate the correct operation and functionality of the prototype chips.<
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