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

• Published in: IEEE transactions on circuits and systems. I, Regular papers Vol. 67; no. 10; pp. 3262 - 3272
• Main Authors: Tannirkulam Chandrasekaran, Sanjeev, Kapoor, Gaurav, Sanyal, Arindam
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: band-pass analog-to-digital converter; Band-pass filters; Bandpass; Calibration; Complex NTF; Configurations; Finishes; Mathematical model; Maximum likelihood estimation; Maximum likelihood estimators; Notches; NTF re-configuration; Quantization (signal); Residues; Resonators; SAR; Thermal noise; Transfer functions
• ISSN: 1549-8328; 1558-0806
• DOI: 10.1109/TCSI.2020.2987533

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 <inline-formula> <tex-math notation="LaTeX">17~\mu \text{W} </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">85\times </tex-math></inline-formula> better than state-of-the-art BP ADCs with similar bandwidth and <inline-formula> <tex-math notation="LaTeX">8.7\times </tex-math></inline-formula> better than all reported state-of-the-art BP ADCs.