A Third-Order noise-shaping SAR ADC With optimized NTF Zeros for IoT Applications

This article presents a fully dynamic, simple, and area-efficient third-order noise shaping successive approximation register analog to digital converter (NS-SAR ADC) that is suitable for the internet of thing (IoT) applications. This work utilizes a passive integrator in the feed-forward (FF) path of a second-order error-feedback (EF) NS-SAR ADC to enhance its in-band quantization noise suppression effect. This integrator is very simple and area-efficient because built just with a switch and a capacitor. Integrator attenuation arising from charge-sharing is compensated with embedded comparator relative gain of 4. The noise transfer function (NTF) zeros are optimized. In this work sampling frequency, bandwidth, and over-sampling ratio (OSR) are 3.2 MS/S, 200kHz, and S respectively. The proposed structure is investigated systematically by MATLAB software. Using the proposed technique, a 3rd order NS-SAR ADC is obtained and the signal to noise and distortion ratio (SNDR) of the ADC is enhanced from 94.7dB to 104.3dB.