A 2nd-Order Noise Shaping SAR ADC Realizing NTF Zero-Pole Optimization Based on IIR-FIR Filter

This paper reports a successive approximation register (SAR) analog-to-digital converters (ADCs) with the 2nd-order and optimized noise shaping (NS) scheme. Based on the feed-forward structure, both noise transfer function (NTF) zero and pole optimization have been achieved simultaneously utilizing a cascaded IIR-FIR (infinite impulse response and finite impulse response) filter. The analysis shows that the proposed structure provides a better NS efficiency than prior arts. The efficiency of the proposed NS scheme and the ADC performance are verified by simulation achieving a 14.2 effective number of bits with an 8-bit SAR ADC architecture at an over sampling rate of 8 sampled at 100 MS/s. Taking advantage of the NTF zero-pole optimization, a low resolution SAR ADC is allowed under the same quantization noise budget in this structure.