Compact two-dimensional CMOS Hall sensor based on switchable configurations of four three-contact elements

This paper reports a novel CMOS sensor of compelling design simplicity for the measurement of both in-plane magnetic field components Bx and By at the same location. The device is operated through only four contacts and using a single control signal. It consists of four separate n-wells arranged as two orthogonal pairs. Each n-well segment forms a three-contact vertical Hall element (3CVHE) whose two outer contacts are used for the electrical interconnection of the four 3CVHEs into a conducting loop. The central contacts of each 3CVHE serve as drive and sense contacts enabling offset reduction by the spinning-current method. The operating principle of the novel device is derived from the magnetic field dependent resistance matrix of the individual 3CVHEs. The two-axis sensing capability of the sensor is achieved by selectively switching the interconnections among the four 3CVHEs, whereby the device is made sensitive alternatingly to Bx and By. Integrated transmission gates (TG) serve as switches. Appropriate design ensures the electrical symmetry of the sensor, which results in a low equivalent offset field of 0.2 to 0.4 mT. For a nominal B field of 3.7 mT the RMS error of the measured magnitude and angle of B are extracted to be only 42 μT and 0.7°, respectively.