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

In this work we propose a single channel bandpass (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 17μW from a 1V supply at 2.43MS/s. The ADC core occupies an area of 0.12mm
²
. The ADC achieves 8fJ/c-step bandpass FoM which is 85× better than state-of-the-art BP ADCs with similar bandwidth and 8.7× better than all reported state-of-the-art BP ADCs.