A 20kHz 87.2dB SNDR 12.1µW NS SAR ADC Based on Quantization-Error-Matched RLSB-First Algorithm

Most noise shaping (NS) SAR ADCs still use the same control algorithm as Nyquist SAR ADC. Noticing the slow-varying input under oversampling, this paper proposed a new algorithm named quantization-error-matched RLSB-first to improve the switching efficiency. Compared with the VCM-based algorithm, the proposed algorithm saves 87.3 % switching power consumption in a 1^st order NS SAR under an OSR of 25. Simulated under a 55nm CMOS process, the NS SAR ADC based on the proposed algorithm achieves an SNDR of 87.2dB with a 20kHz signal bandwidth. Operating at 2.8kS/s sampling rate, it consumes 12.1µW power, corresponding to a Schreier FoM of 179.4dB.