Vertical Hall sensors typically comprise a Hall effect region that is formed within a substrate, such as a semiconductor substrate. Vertical Hall sensors respond to magnetic field components parallel to the substrate or, more precisely, parallel to a main surface of the substrate.
Typically, vertical Hall sensors have one problem in common, namely an offset error. The offset is the output signal in the absence of the magnetic field or the component thereof which the sensor should detect. The origin of the offset error is basically a slight asymmetry of the device. The so-called spinning current technique may be used to reduce the offset error of Hall devices. The spinning current technique was initially devised to be applied to horizontal Hall devices or “Hall plates”: in subsequent clock phases the roles of supply and sense terminals of the Hall plate are exchanged. The output signals of the Hall plate in two clock phases are added or subtracted so that the offset (i.e., the zero point error) cancels and a strong signal with respect to the prevailing magnetic field remains.
The offset cancellation works all the better the higher the symmetry of the Hall plate or Hall device is. Therefore, Hall plates typically have a 90° symmetry, for example, squares, crosses or octagons. Vertical Hall devices on the other hand are typically less symmetric and therefore spinning current techniques are not as efficient for vertical Hall devices than for Hall plates (horizontal Hall devices).
USPTO Backgrounds
USPTO Backgrounds