A Second-Order Passive Noise-Shaping SAR ADC Using the LMS-Based Mismatch Calibration

Jing Li, Hang Xiao, Qihui Zhang, Zhong Zhang, Wenjie Huang, Ning Ning, Qi Yu

Abstract: A second-order passive noise-shaping (NS) SAR ADC using the LMS-based mismatch calibration is proposed in this paper. This structure suppresses low-frequency noise through second-order noise-shaping. By separating two passive integrators with a pre-amplifier, the area of the second-stage integrator can be reduced. In addition, the mismatch calibration technique based on (least mean square) LMS algorithm is applied to this NS SAR ADC. After calibration, the impact of capacitance mismatch on ADC performance is reduced. A prototype 9-bit NS-SAR ADC is designed and simulated in a 130-nm CMOS process. At an oversampling ratio (OSR) of 8, it achieves 78.04 dB signal to noise and distortion ratio (SNDR) and 96.5 dB spurious free dynamic range (SFDR) with calibration. The overall architecture consumes 65.3 μW when operating at 2MS/s sampling frequency.