A13b-ENOB Third-Order Noise-Shaping SAR ADC using a Hybrid Error-Control Structure

Qihui Zhang, Jing Li, Zhong Zhang, Kejun Wu, Ning Ning, Qi Yu

Abstract: The Noise shaping (NS) SAR ADC combines the merits of both SAR and ΔΣ ADCs, which provides high resolution with high energyefficiency and compactness. To realize a prominent noise transfer function (NTF), most existing designs adopted the cascaded integrator feed-forward (CIFF) structure [1-3] or the error-feedback (EF) architecture [4] for the noise filtering. However, the difficulty of implementing an NS loop filter increases dramatically with the growth of the NTF order (beyond 3). The CIFF NS SAR needs to cascade more integrators, which consumes higher power and occupies a larger silicon area. For the EF NS SAR, the excessive and vulnerable FIR filter coefficients require more delay cells and stable residual amplifiers. Many NS SARs that require 13b-ENOB are built with quantizers > =9-bit due to the restriction of a low-order NTF.