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This microsystem is the key element for accurate contactless angle measurements in combination with a permanent magnet (Figure la). The system is based on a novel approach for signal processing using an on-board incremental ADC and a two-dimensional (2D) magnetic microsensor allowing 1" resolution. The system can be used for various wear-free angular positioning control systems in industrial and automotive applications.Commercially available magnetic angle measurement systems are based either on magnetoresistive sensors or on two orthogonally mounted Hall sensors, whereas the sensing element in the system presented here exploits galvanomagnetic effects in silicon using one single device. This approach permits superior performance. First, the sensing element has a much smaller sensitive area (30x30pm2), allowing field distribution to be considered as homogeneous even for very small permanent magnets. This feature is important for accurate angle sensing and aLIows a compact integration of the complete sensor-magnet system. Second, the galvanomagnetic effect in silicon is linear, allowing unrestricted angle measurement over the full 360" range. Next, the sensing element detects both orthogonal field components simultaneously making the angle detection unique and independent of the magnitude of the applied magnetic field. Finally, the CMOS compatibility of the sensor allows cost-effective batch fabrication and integration of on-chip biasing and readout circuitry.The system consists of a 2D magnetic microsensor, a biasing circuit, two 10b D/A converters performing offset compensation, and a signal processing circuit capable of calculating the ratio of the two field components parallel to the chip plane. The output of the system is a bitstream that represents the angular position of the permanent magnet. The angle is measured over the full 360" range with a resolution of 1". A block diagram of the implemented system is shown in Figure l b The sensing element is a lateral magnetotransistor (LMT) with four collectors. The performance of the LMT has been optimized following the design guidelines [l]. Sensor layout and cross section are shown in Figure 2. A magnetic induction parallel to the chip plane leads to an imbalance of the collector currents. The resulting current differences Icl -Ic3 and I, -I, are proportional to the magnetic field components Bx and By, respectively. Due to unavoidable lithographical imperfections and process-induced stress (piezoresistive effect) the LMT exhibits an original offset up to 2200mT. This offset is compensated after packaging and mounting of the device by means of a compensation cycle with the dual on-chip 10b D/A converter (for the X and the Y component of the sensor). The circuit for biasing and offset compensation is shown in Figure 3.The matching of the sensitivities SI= I,l-I$3i, i = x, y is a limiting factor of the system accuracy since the ratio of the two field components defines the angle. 10 devices characterized show worst-case deviation of less than 2%, allowing an angula...

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