Contactless 360° absolute angular CMOS microsystem based on vertical Hall sensors.pdf

Sensors and Actuators A 116 (2004) 39–44 Contactless 360 ? absolute angular CMOS microsystem based on vertical Hall sensors Michel Demierre a,? , Enrico Schurig a , Christian Schott b , Pierre-André Besse a , Radivoje S. Popovic? a a Swiss Federal Institute of Technology, Institute of Microelectronics and Microsystems, CH-1015 Lausanne, Switzerland b SENTRON AG, CH-6300 Zug, Switzerland Received 28 April 2003; received in revised form 15 March 2004; accepted 18 March 2004 Available online 10 May 2004 Abstract We have developed the first 360 ? contactless absolute angular microsystem using a CMOS two-dimensional vertical Hall sensor. The microsystem contains two groups of vertical Hall sensors, mutually oriented at 90 ? , and complete readout electronics. The spinning current method is used to extract the signals from the sensors. Projections onto two orthogonal axes of the external rotating magnetic field give the rotation angle sine and cosine functions, respectively. From these two output signals, the rotation angle is extracted using the four quadrant inverse tangent function without discontinuity or dead angle over 360 ? . An angular accuracy of less than ±0.5?(±0.14%) at room temperature with only the Hall sensors’ residual offset compensation is obtained. Using gain mismatch and phase compensation, an outstanding accuracy of ±0.17?(±0.05%) is achieved. ? 2004 Elsevier B.V. All rights reserved. Keywords: Hall; Vertical; CMOS; Magnetic sensors; Angular; Contactless 1. Introduction Angular sensors are widely used in automotive, indus- trial, and consumer applications. They are based on various principles, including mechanical, resistive, optical, capaci- tive, inductive, and magnetic [1]. Magnetic angular sensors have the advantages of contactless measurement, reliability in harsh environments and low cost. Two magnetoresistances such as AMR [2] and GMR [3] placed orthogonally were used for contactless 360 ? angle measurement. This technology is unfortunately not