8fJ/Step Bandpass ADC With Digitally Assisted NTF Re-Configuration

Abstract

In this work we propose a single channel band-pass (BP) SAR ADC with dynamic noise transfer function (NTF) re-configuration. The proposed ADC employs a low-power two-stage architecture. After the SAR finishes quantization, the residue is extracted by firing the comparator multiple times. An estimate of the residue is obtained by employing a maximum likelihood based estimator (MLE). The output of the ADC is obtained by subtracting a delayed version of the estimated residue from the SAR output thus generating a complex NTF with multiple notches in the spectrum. A 65nm ADC prototype achieves 74.1/78dB SNDR/DR over a 101.2kHz bandwidth while consuming $17~\mu \text{W}$ from a 1V supply at 2.43MS/s. The ADC core occupies an area of 0.12mm2. The ADC achieves 8fJ/c-step bandpass FoM which is $85\times $ better than state-of-the-art BP ADCs with similar bandwidth and $8.7\times $ better than all reported state-of-the-art BP ADCs.