A Low-Spur MASH Delta-Sigma Modulator With an Adaptive Length Extension Technique

This brief presents a novel multistage noise-shaping (MASH) delta-sigma modulator that has low spurs for all input values by the proposed adaptive length extension technique. Based on the feedforward structure, the accumulators in the proposed MASH are fully utilized to realize an adaptive feedforward gain to compensate for the sequence length loss due to input. The proposed MASH can extend the output sequence length to the maximum under any input, thus to reduce spurs. Simulation results show that the quantization noise of the proposed MASH is distributed widely with no noticeable spurs. Synthesized with 180nm CMOS technology, the increase in hardware cost of the proposed MASH is slight.