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CESG Seminar: Scaling-Friendly VCO-Based ADC Design in Advanced CMOS Processes

April 17, 2015 @ 3:55 pm - 5:00 pm

room 1037 ETB

Nan Sun (The University of Texas at Austin)

Abstract: The conventional way to build ADCs relies on the use of voltage comparators and OTA-based analog integrators. This design methodology encounters severe difficulties in advanced nanometer-scale CMOS processes due to reduced power supply voltages and transistor intrinsic gains. Recently, there have been emerging efforts to use ring voltage-controlled oscillators (VCOs) to build ADCs, as they are simple to design, area/power efficient, and scaling friendly. As technology scales, the VCO-based quantizer resolution naturally improves due to reduced inverter delay.

In this talk, I will review the state-of-the-art and present our recent development of two novel VCO-based ADC architectures. The first one is a VCO-based closed-loop continuous-time ADC. It uses VCOs as both quantizers and integrators, and thus, obviates the need for power-hungry and area-consuming OTAs and precision comparators. It arranges two VCOs in a pseudo-differential manner so that the even-order distortions are cancelled out. Moreover, it brings an intrinsic dynamic element matching (DEM) capability that shifts the majority of the DAC mismatch error out of the signal band without increasing hardware cost and loop delay. The second architecture is a hybrid two-stage 0-1 MASH ADC that combines a first-stage SAR and a second-stage VCO. The SAR ADC has very good power efficiency at low resolution, while the VCO can provide fine quantization for the SAR residue without the need for OTA-based residue amplification. Thus, combining a SAR with a VCO can reap the benefits of both ADCs, leading to a scaling-friendly high-resolution architecture.

Bio: Nan Sun is an Assistant Professor in the Department of Electrical and Computer Engineering at the University of Texas at Austin. He received the B.S. degree from Tsinghua University, Beijing, China in 2006, where he ranked top in the Department of Electronic Engineering and graduated with the highest honor and the Outstanding Undergraduate Thesis Award. He received the Ph.D. degree from the School of Engineering and Applied Sciences at Harvard University in 2010.

Dr. Sun received the NSF Career Award in 2013. He also received Samsung Fellowship, Hewlett Packard Fellowship, and Analog Devices Outstanding Student Designer Award in 2003, 2006, and 2007, respectively. He won Harvard Teaching Award in three consecutive years: 2008, 2009, and 2010. He serves in the TPC of Asian Solid-State Circuit Conference.

His research interests include: 1) analog, mixed-signal, and RF integrated circuits; 2) miniature spin resonance systems; 3) magnetic sensors and image sensors; 4) developing micro- and nano-scale solid-state platforms (silicon ICs and beyond) to analyze biological systems for biotechnology and medicine.

Host: Dr. Khatri



April 17, 2015
3:55 pm - 5:00 pm