Tutorials / Short Courses

2015 IEEE International Symposium on Circuits and Systems (Nuit de la litterature 2015)

Sunday, 21 May 2015


A9: Time-Continuous Delta-Sigma A/D Converters - From Theory to Practical Implementation

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13:30 - 17:30



A successful implementation of a time-continuous (CT) Delta-Sigma A/D converter is anything but a simple task. From signal processing over communication theory up to circuit design, many classical disciplines are involved in the design process for this kind of an A/D converter. A deep understanding of all of these disciplines, even more of their interaction is the prerequisite not only for the comprehension of Delta-Sigma A/D converters but also for their successful implementations. But even with all this knowledge, designing a Delta-Sigma A/D converter still remains a great challenge these days. In times, when supply voltages are sinking below the 1V barrier and therewith rendering classical concepts such as gain enhancement via cascode transistors useless, circuit designers in the field of A/D converters have to deal with the demands of ever-growing resolution and bandwidth along with lower power consumption. Having turned out to be tolerant to most of the circuit non-idealities afflicted with deep-submicron CMOS technologies over the last decades, CT Delta-Sigma modulators seem to be a most promising solution to these demands. While their power consumption is considerably lower compared to their time-discrete equivalents and in general to any other type of A/D converters due to the lower bandwidth requirements of the operational amplifiers, they hold the additional advantage of an implicit anti-aliasing filter. Moreover, prototypes of CT implementations for baseband signal bandwidths up to a few tenths of megahertz have already been reported.

This tutorial is therefore intended to give a deep insight into these converters and especially into their core, the Delta-Sigma modulator. With its main focus on baseband applications, aspects such as architecture choice (single-stage, multi-stage, single-bit, multi-bit), stability analysis, implicit anti-aliasing filter, influence of circuit non-idealities, compensation approaches for the latter and practical design guidelines under the aspects of low power and low voltage will be covered, all of them illustrated by implementations either from the academic or the industrial field.


Welcome / Introduction

Prof. Dr.-Ing. Yiannos Manoli, University of Freiburg

1. Architectures for baseband applications (single-stage, multi-stage), stability considerations

Dipl. Ing. Alexander Buhmann, University of Freiburg

2. Implicit anti-aliasing filter

Dipl. Ing. Matthias Keller, University of Freiburg

3. Influence of non-idealities and their correction techniques

Dr.-Ing. Maurits Ortmanns, sci-worx

4. Implementation (low power, ultra wideband, high performance)

Dr.-Ing. Friedel Gerfers, Philips


Prof. Dr.-Ing. Yiannos Manoli, University of Freiburg

Short Biographies

Yiannos Manoli (M82) received the B.A. degree (summa cum laude) in physics and mathematics from Lawrence University, Appleton, WI, in 1978, the M.S. degree in electrical engineering and computer science from the University of California, Berkeley, in 1980, and the Dr.-Ing. degree in electrical engineering from the Gerhard Mercator University, Duisburg, Germany, in 1987.

From 1980 to 1984, he was with the University of Dortmund, Germany, working in the field of digital and analog MOS integrated circuit design with an emphasis on A/D and D/A converters. In 1985, he joined the Fraunhofer Institute of Microelectronic Circuits and Systems, Duisburg, where he established a design group for microsystem and microcontroller integrated circuits. In 1996, he joined the Department of Electrical Engineering, Saarland University, Germany, where he held the Chair of Microelectronics. In July 2005, he was appointed Chair of Microelectronics at the Department of Microsystems Engineering (IMTEK) of the University of Freiburg, Germany. His current research interests are the design of low-voltage/low-power mixed-signal CMOS circuits, sensor read-out, and A/D and D/A converters. Prof. Manoli has served on the committees of a number of conferences and was Program Chair (2005) and General Chair (2015) of the IEEE International Conference on Computer Design (ICCD). He is a member of Mortar Board, Phi Beta Kappa, VDE, and VDI.

Maurits Ortmanns (S04M05) received the Dipl.-Ing. (M.Sc.) in electrical engineering from the Saarland University, Germany, in 1999 and the Dr.-Ing. (Ph.D.) degree for his dissertation Error Compensation in CT Sigma-Delta A/D Converters from the University of Freiburg, Germany, in 2008, both with highest honors.

Since April 2008, he has been with sci-worx GmbH, Hannover, Germany, where he is currently working in the field of mixed-signal and analog circuits for biomedical implants, low-voltage, low-power applications, and high-speed circuits. His main research interests include mixed-signal circuit design, smart microsensors, and biomedical applications.

Friedel Gerfers (S02M04) received the Dipl.-Ing. (M.Sc.) degree in electrical engineering from the Gerhard-Mercator-University, Duisburg, Germany, in 1996 and the Dr.-Ing. (Ph.D.) degree for his dissertation Design Strategy, Limits and Implementation of Low-Voltage, Low- Power CT Sigma-Delta Modulators from the University of Freiburg, Germany, in 2009.

Since April 2007, he has been with Philips Semiconductor Starnberg, Germany, where he is currently working on low-power high-speed CDR circuits and high-speed ADCs for video processing interfaces, scalar chips and high-speed data communication links. His main research interests are low-voltage low-power analog circuit design, sigma-delta modulation, A/D conversion, clock and data recovery circuits and sensor readout.

Matthias Keller (S04) received the Dipl.-Ing. (M.Sc.) degree in electrical engineering from the Saarland University, Germany, in 2007. In 2007, he joined the Department of Microsystems Engineering, University of Freiburg, where he is currently working as a research assistant at the chair of microelectronics. With his main research interests focused on analog/mixed-signal circuit design and A/D converters, he is working toward the Ph.D. degree in the field of time-continuous Delta-Sigma A/D converters.

Alexander Buhmann (S04) received the Dipl.-Ing. degree from the University of Freiburg, Germany, in 2007. He is currently pursuing the Ph.D. degree at the Department of Microsystems Engineering, University of Freiburg. His current research interests include sensors and systems, control theory and algorithm development.


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