Series in MICROSYSTEMS
edited by P. A. Besse,
R. S. Popovic,
Predrag M. Drljaca,
Integrated Fluxgate Compass for Portable Applications.
2004, 254 p., € 64,00. ISBN 3-89649-958-0
This book describes the design and fabrication of an integrated electronic compass working on the fluxgate principle. The fabricated sensor works from a single 2.5 V power supply and consumes 10 mW, which makes it suitable for portable applications. It is a fully integrated device based on CMOS process that provides driving and readout electronics, plus the metallization layers for the excitation and pickup coils. A soft amorphous ferromagnetic material is bonded and structured, using an additional, post-process implemented on a whole 6 inch wafer to form sensor core on the surface of the chip. Several models and tools for the optimization of the core geometry, excitation, as well as pickup coils have been developed and used to establish the design rules for high sensitivity and low power sensor. The book presents measurements and elaborate mechanisms causing the perming effect in planar open core fluxgates. The electronics has been integrated in a conventional 1m m CMOS process. Apart from the excitation, a single circuit is used for both axes in order to decrease the power consumption, reduce the chip size and obtain better matching. The signal extraction principle is accomplished using a box-car circuit and a correlated double sampling. To ensure matching of the axes sensor uses a feedback that consists of comparator, 8bit up/down counter and current sources. The output of the counter represents the digital information on the external field and is transmitted using I2C communication block integrated on chip. With high performance and low cost fabrication we can expect commercialization in the near future.
Predrag M. Drljaca, was born in Belgrade, Serbia, in 1972. He obtained his B.Sc. and Ms. Sc. degree in Electrical Engineering from the University of Belgrade, Yugoslavia in 1996 and 1999 respectively. From 1997 to 1999 he has been working as research and teaching assistant at the Department of Microelectronics and Engineering Physics, the University of Belgrade. Since 2000 he has joined the Institute of Microelectronics and Microsystems at the Swiss Federal Institute of Technology in Lausanne (EPFL) as a research and teaching assistant. In 2004 he obtained his Ph.D. for his work on low power micro-fluxgate magnetometer. His current research interests include noise and nonlinear effects in magnetic sensor micro-systems.
Keywords: compass, fluxgate, CMOS, magnetometer, ferromagnetic materials, perming
Series in MICROSYSTEMS
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