A 14bit 80kHz SigmaDelta A/D Converter: Modeling, Design, and Performance Evaluation

This paper describes the development of a sigma-delta A/D converter. Included is a brief overview of sigma-delta conversion. The A/D) converter achieves an 88.5-dB dynamic range and a maximum signal-to-noise ratio of 81.5 dB. The harmonic distortion is negligible. This level of performance is about 10 dB higher than previously reported results for oversampled A/D converters in this frequency range [1], [2]. The analog modulator employs a double-integration switched-capacitor architecture with an oversampling rate of 10.24 MHz. Transconductance amplifiers having a 160-MHz ft were developed for the integrators. The circuit is implemented in a 1.75-¿m 5-V CMOS process. The analog circuitry occupies 2 mm² of silicon area and consumes 75 mW of power. Some of the difficult problems associated with evaluating the performance of sigma-delta converters are described. The design of a sigma-delta development and performance evaluation system is presented. This system includes a custom interface board linking the chip to a Sun workstation, and extensive digital signal processing and analysis software.