A multi-bit sigma-delta ADC for multi-mode receivers

Abstract

A 2.7-volt /spl Sigma//spl Delta/ modulator with a 6-bit quantizer is fabricated in a 0.18 /spl mu/m CMOS process. The modulator makes use of noise-shaped dynamic element matching and quantizer offset chopping to attain high linearity over a wide bandwidth. The circuit achieves 95 dB peak SFDR and 77 dB SNR over a 625 kHz bandwidth and consumes 30 mW at a sampling frequency of 23 MHz. Further, it achieves 70 dB SNR over a 1.92 MHz bandwidth and dissipates 50 mW when clocked at 46 MHz.