The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Integrated Reference Circuits for Low-Power Capacitive Sensor Interfaces

Matti Paavola

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium S4 at the Aalto University School of Science and Technology (Espoo, Finland) on the 1st of October 2010 at 12 noon.

Overview in PDF format (ISBN 978-952-60-3319-8)   [1569 KB]
Dissertation is also available in print (ISBN 978-952-60-3318-1)

Abstract

This thesis consists of nine publications and an overview of the research topic, which also summarizes the work. The research described in this thesis concentrates on the design of low-power sensor interfaces for capacitive 3-axis micro-accelerometers. The primary goal throughout the thesis is to optimize power dissipation. Because the author made the main contribution to the design of the reference and power management circuits required, the overview part is dominated by the following research topics: current, voltage, and temperature references, frequency references, and voltage regulators.

After an introduction to capacitive micro-accelerometers, the work describes the typical integrated readout electronics of a capacitive sensor on the functional level. The readout electronics can be divided into four different functional parts, namely the sensor readout itself, signal post-processing, references, and power management. Before the focus is shifted to the references and further to power management, different ways to realize the sensor readout are briefly discussed.

Both current and voltage references are required in most analog and mixed-signal systems. A bandgap voltage reference, which inherently uses at least one current reference, is practical for the generation of an accurate reference voltage. Very similar circuit techniques can be exploited when implementing a temperature reference, the need for which in the sensor readout may be justified by the temperature compensation, for example.

The work introduces non-linear frequency references, namely ring and relaxation oscillators, which are very suitable for the generation of the relatively low-frequency clock signals typically needed in the sensor interfaces. Such oscillators suffer from poor jitter and phase noise performance, the quantities of which also deserve discussion in this thesis.

Finally, the regulation of the supply voltage using linear regulators is considered. In addition to extending the battery life by providing a low quiescent current, the regulator must be able to supply very low load currents and operate without off-chip capacitors.

This thesis consists of an overview and of the following 9 publications:

  1. Matti Paavola, Mika Laiho, Mikko Saukoski, and Kari Halonen. 2006. A 3 µW, 2 MHz CMOS frequency reference for capacitive sensor applications. In: Proceedings of the 2006 IEEE International Symposium on Circuits and Systems (ISCAS 2006). Kos, Greece. 21-24 May 2006. Pages 4391-4394. ISBN 0-7803-9390-2. © 2006 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  2. Matti Paavola, Mikko Saukoski, Mika Laiho, and Kari Halonen. 2007. A micropower voltage, current, and temperature reference for a low-power capacitive sensor interface. In: Proceedings of the 2007 IEEE International Symposium on Circuits and Systems (ISCAS 2007). New Orleans, LA, USA. 27-30 May 2007. Pages 3067-3070. ISBN 1-4244-0921-7. © 2007 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  3. Matti Paavola, Mika Kämäräinen, Jere Järvinen, Mikko Saukoski, Mika Laiho, and Kari Halonen. 2007. A 62µA interface ASIC for a capacitive 3-axis micro-accelerometer. In: Digest of Technical Papers of the 2007 IEEE International Solid-State Circuits Conference (ISSCC 2007). San Francisco, CA, USA. 11-15 February 2007. Pages 318-319, 605. ISBN 1-4244-0852-0. © 2007 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  4. Matti Paavola, Mika Kämäräinen, Jere A. M. Järvinen, Mikko Saukoski, Mika Laiho, and Kari A. I. Halonen. 2007. A micropower interface ASIC for a capacitive 3-axis micro-accelerometer. IEEE Journal of Solid-State Circuits, volume 42, number 12, pages 2651-2665. © 2007 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  5. Mika Kämäräinen, Matti Paavola, Mikko Saukoski, Erkka Laulainen, Lauri Koskinen, Marko Kosunen, and Kari Halonen. 2008. A 1.5µW 1V 2nd-order ΔΣ sensor front-end with signal boosting and offset compensation for a capacitive 3-axis micro-accelerometer. In: Digest of Technical Papers of the 2008 IEEE International Solid-State Circuits Conference (ISSCC 2008). San Francisco, CA, USA. 3-7 February 2008. Pages 578-579, 637. ISBN 978-1-4244-2011-7. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  6. Matti Paavola, Mika Kämäräinen, Mikko Saukoski, and Kari Halonen. 2008. A micropower low-dropout regulator with a programmable on-chip load capacitor for a low-power capacitive sensor interface. In: Proceedings of the 15th IEEE International Conference on Electronics, Circuits and Systems (ICECS 2008). St. Julian's, Malta. 31 August - 3 September 2008. Pages 450-453. ISBN 978-1-4244-2182-4. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  7. Matti Paavola, Mika Kämäräinen, Erkka Laulainen, Mikko Saukoski, Lauri Koskinen, Marko Kosunen, and Kari Halonen. 2008. A 21.2µA ΔΣ-based interface ASIC for a capacitive 3-axis micro-accelerometer. In: Proceedings of the 2008 IEEE Asian Solid-State Circuits Conference (A-SSCC 2008). Fukuoka, Japan. 3-5 November 2008. Pages 101-104. ISBN 978-1-4244-2605-8. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  8. Matti Paavola, Mika Kämäräinen, Erkka Laulainen, Mikko Saukoski, Lauri Koskinen, Marko Kosunen, and Kari A. I. Halonen. 2009. A micropower ΔΣ-based interface ASIC for a capacitive 3-axis micro-accelerometer. IEEE Journal of Solid-State Circuits, volume 44, number 11, pages 3193-3210. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  9. M. Paavola, M. Laiho, M. Saukoski, M. Kämäräinen, and K. A. I. Halonen. 2010. Impulse sensitivity function-based phase noise study for low-power source-coupled CMOS multivibrators. Analog Integrated Circuits and Signal Processing, volume 62, number 1, pages 29-41. © 2009 Springer Science+Business Media. By permission.

Errata of publications 1, 5, 8 and 9

Keywords: capacitive accelerometer, complementary metal-oxide-semiconductor (CMOS), power management circuit, reference circuit, sensor interface

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Last update 2011-05-26