A CMOS Oversampling A/D Converter With 12b Resolution At Conversion Rates Above 1Mhz

Oversampling analog-to-digital converters based on sigma delta (ΣΔ) modulation have previously been used for high-precision signal acquisition in voiceband telecommunications, digital audio, and ISDN applications. This work examines the application of oversampling techniques to analog-to-digital conversion at rates above 1MHz. The potential advantages of an oversampling approach include improved tolerance of component mismatch, relaxed antialiasing filter requirements, elimination of precision sample-and-hold circuitry, and digital filtering capability. This paper introduces a ΣΔ modulator architecture that substantially reduces the oversampling ratio required for 12b resolution while avoiding stringent component matching requirements. At an oversampling ratio of24 and a sampling rate of 50MHz, an experimental implementation of the modulator in a lµm CMOS technology achieves a dynamic range of 7 4dB at a conversion rate of 2. lMHz.