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 Interface Electronics for Capacitive MEMS Inertial Sensors

Lasse Aaltonen

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 29th of October 2010 at 12 noon.

Overview in PDF format (ISBN 978-952-60-3366-2)   [1869 KB]
Dissertation is also available in print (ISBN 978-952-60-3365-5)

Abstract

This thesis is composed of 13 publications and an overview of the research topic, which also summarizes the work. The research presented in this thesis concentrates on integrated circuits for the realization of interface electronics for capacitive MEMS (micro-electro-mechanical system) inertial sensors, i.e. accelerometers and gyroscopes. The research focuses on circuit techniques for capacitive detection and actuation and on high-voltage and clock generation within the sensor interface.

Characteristics of capacitive accelerometers and gyroscopes and the electronic circuits for accessing the capacitive information in open- and closed-loop configurations are introduced in the thesis. One part of the experimental work, an accelerometer, is realized as a continuous-time closed-loop sensor, and is capable of achieving sub-micro-g resolution. The interface electronics is implemented in a 0.7-µm high-voltage technology. It consists of a force feedback loop, clock generation circuits, and a digitizer. Another part of the experimental work, an analog 2-axis gyroscope, is optimized not only for noise, but predominantly for low power consumption and a small chip area. The implementation includes a pseudo-continuous-time sense readout, analog continuous-time drive loop, phase-locked loop (PLL) for clock generation, and high-voltage circuits for electrostatic excitation and high-voltage detection. The interface is implemented in a 0.35-µm high-voltage technology within an active area of 2.5 mm2. The gyroscope achieves a spot noise of 0.015 °/s/√H̅z̅  for the x-axis and 0.041 °/s/√H̅z̅  for the y-axis.

Coherent demodulation and discrete-time signal processing are often an important part of the sensors and also typical examples that require clock signals. Thus, clock generation within the sensor interfaces is also reviewed. The related experimental work includes two integrated charge pump PLLs, which are optimized for compact realization but also considered with regard to their noise performance. Finally, this thesis discusses fully integrated high-voltage generation, which allows a higher electrostatic force and signal current in capacitive sensors. Open- and closed-loop Dickson charge pumps and high-voltage amplifiers have been realized fully on-chip, with the focus being on optimizing the chip area and on generating precise spurious free high-voltage signals up to 27 V.

This thesis consists of an overview and of the following 13 publications:

  1. Lasse Aaltonen, Pasi Rahikkala, Mikko Saukoski, and Kari Halonen. 2009. High-resolution continuous-time interface for micromachined capacitive accelerometer. International Journal of Circuit Theory and Applications, volume 37, number 2, pages 333-349. © 2009 John Wiley & Sons. By permission.
  2. Lasse Aaltonen and Kari Halonen. 2009. Continuous-time interface for a micromachined capacitive accelerometer with NEA of 4µg and bandwidth of 300Hz. Sensors and Actuators A: Physical, volume 154, number 1, pages 46-56. © 2009 Elsevier Science. By permission.
  3. Lasse Aaltonen and Kari Halonen. 2008. High resolution analog-to-digital converter for low-frequency high-voltage signals. 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 1245-1248. ISBN 978-1-4244-2182-4. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  4. L. Aaltonen and K. Halonen. 2008. Integrated high-voltage PID controller. In: Proceedings of the 11th International Biennial Baltic Electronics Conference (BEC 2008). Tallinn, Estonia. 6-8 October 2008. Pages 125-126. ISBN 978-1-4244-2060-5. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  5. Lasse Aaltonen, Timo Speeti, Mikko Saukoski, and Kari Halonen. 2009. An interface for a 300°/s capacitive 2-axis micro-gyroscope with pseudo-CT readout. In: Digest of Technical Papers of the 2009 IEEE International Solid-State Circuits Conference (ISSCC 2009). San Francisco, CA, USA. 8-12 February 2009. Pages 344-345. ISBN 978-1-4244-3457-2. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  6. Lasse Aaltonen and Kari A. I. Halonen. 2009. Pseudo-continuous-time readout circuit for a 300°/s capacitive 2-axis micro-gyroscope. IEEE Journal of Solid-State Circuits, volume 44, number 12, pages 3609-3620. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  7. L. Aaltonen and K. A. I. Halonen. 2010. An analog drive loop for a capacitive MEMS gyroscope. Analog Integrated Circuits and Signal Processing, volume 63, number 3, pages 465-476. © 2009 Springer Science+Business Media. By permission.
  8. Lasse Aaltonen and Kari Halonen. 2009. On-chip charge-pump with continuous frequency regulation for precision high-voltage generation. In: Proceedings of the 2009 Ph.D. Research in Microelectronics and Electronics (PRIME 2009). Cork, Ireland. 12-17 July 2009. Pages 68-71. ISBN 978-1-4244-3732-0. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  9. Timo Speeti, Lasse Aaltonen, and Kari Halonen. 2009. Integrated charge-pump phase-locked loop with SC-loop filter for capacitive microsensor readout. In: Proceedings of the 2009 IEEE International Symposium on Circuits and Systems (ISCAS 2009). Taipei, Taiwan. 24-27 May 2009. Pages 1373-1376. ISBN 978-1-4244-3828-0. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  10. Lasse Aaltonen, Mikko Saukoski, and Kari Halonen. 2005. Design of clock generating fully integrated PLL using low frequency reference signal. In: Proceedings of the 17th European Conference on Circuit Theory and Design (ECCTD 2005). Cork, Ireland. 28 August - 2 September 2005. Volume 1, pages 161-164. ISBN 0-7803-9066-0. © 2005 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  11. L. Aaltonen, M. Saukoski, I. Teikari, and K. Halonen. 2006. Noise analysis of comparator performed sine-to-square conversion. In: Proceedings of the 10th International Biennial Baltic Electronics Conference (BEC 2006). Tallinn, Estonia. 2-4 October 2006. Pages 103-106. ISBN 1-4244-0415-0. © 2006 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  12. Lasse Aaltonen, Mikko Saukoski, and Kari Halonen. 2006. On-chip digitally tunable high voltage generator for electrostatic control of micromechanical devices. In: Proceedings of the 28th IEEE Custom Integrated Circuits Conference (CICC 2006). San Jose, CA, USA. 10-13 September 2006. Pages 583-586. ISBN 1-4244-0076-7. © 2006 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  13. Lasse Aaltonen, Mikko Saukoski, and Kari Halonen. 2005. Fully integrated charge pump for high voltage excitation of a bulk micromachined gyroscope. In: Proceedings of the 2005 IEEE International Symposium on Circuits and Systems (ISCAS 2005). Kobe, Japan. 23-26 May 2005. Pages 5381-5384. ISBN 0-7803-8834-8. © 2005 Institute of Electrical and Electronics Engineers (IEEE). By permission.

Errata of publication 2

Keywords: capacitive sensor, complementary metal-oxide-semiconductor, micro-electro-mechanical system, accelerometer, gyroscope, charge pump, phase-locked loop

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Last update 2011-05-26