Integrated Hall Magnetic Angle Sensors
A magnetic angle sensor is a matched combination of a permanent magnet, affixed to a rotating shaft, and a magnetic field sensor. The magnet part of the angle sensors is configured so as to create either a magnetic field with an angle-dependent component perpendicular to the chip surface; or two angle-dependent components parallel with the chip surface. The magnetic field component perpendicular to the sensor dice is measured by planar Hall devices. The two in-plane magnetic field components are measured either by a combination of planar Hall devices and an integrated magnetic flux concentrator (IMC-Hall), or by vertical Hall devices. The IMC-Hall is the most used technology for implementing a compass in mobile telephones. The circular vertical Hall device is most suitable for high-speed rotation angle sensing. The major performance-limiting factors of magnetic angle sensors are non-uniformity of magnets, imperfections in the integrated magnetic sensor IC, and thermal drift. The magnetic sensing part of contemporary magnetic angle sensors is a CMOS IC, incorporating Hall devices, biasing circuit, amplifiers and other analog signal conditioning circuits, analog-to-digital convertors, and digital circuits for angle retrieval and correction of errors.