A Predictive Noise Shaping SAR ADC with Redundancy

This paper presents a predictive noise shaping (NS) Successive Approximation (SAR) Analogto-Digital Converter (ADC), which improves its conversion speed by 25%, compared to its counterpart with 0.3% less redundancy. It begins by investigating the Signal to Noise and Distortion Ratio (SNDR) degradation when using a lower Oversampling Ratio (OSR, e.g., 8) than required in the prior state-of-the-art works, when predicting the first 4 MSBs with a second-order predictor. Later, it compares the SNDR for the same predictor with and without the bit weight redundancy in the capacitor array. In addition, designs with various levels of redundancies and OSRs are compared on their SNDRs. Both MATLAB and Cadence simulation results verified that by introducing 0.3% more redundant bit weight, either 8 dB more SNDR at the same bandwidth, or 25% speed improvement can be obtained while maintaining its SNDR.