Limits of offset cancellation by the principle of spinning current hall probe

Abstract

An equivalent circuit model for Hall plates with 90° symmetry -as are used in todays smart sensors using the principle of spinning current Hall probe -is derived. It becomes apparent that the commonly used H-bridge 4resistor type equivalent circuit has to be completed by 2 resistors between the contacts of each diagonal. By use of this equivalent circuit it is shown that the principle of spinning current Hall probe works perfectly only for electrically linear probes supplied by a current source. In this case two orthogonal current directions are enough to cancel the offset. Yet, in the case of voltage biased Hall probes the offset is not completely eliminated. In practice, integrated Hall probes exhibit electrical nonlinearity due to the depletion layer to the substrate. Monte Carlo simulations show that this nonlinearity limits the performance of offset reduction to roughly 100nT.

A Theory of Magnetic Angle Sensors With Hall Plates and Without Fluxguides

“…In order not to pose too stringent requirements on the magnet one has to use axialC8 instead of axialC4 systems. An alternative system with similar performance like axialC8 systems is sketched in Appendix D. Applying Maxwell's equations to (12) gives several relations between derivatives, which will be used in the sequel to simplify the angle error. From curl B = 0 one gets ∂B x /∂y = ∂B y /∂x, ∂B y /∂z = ∂B z /∂y, ∂B x /∂z = ∂B z /∂x.…”

“…If the Hall plates are operated in a spinning current scheme [12], the raw offset of about 10 mT is reduced by two to three orders in magnitude so that finally the signals only have a residual offset of about 30 µT. If the B z -field is 30 mT at each Hall plate the signals are …”

“…As sensor elements one can use horizontal Hall plates (HHall) [9,10] or MAGFETs [11]. The main advantage is the mature technology of HHalls, where the problems of offset [12] and mechanical stress [13,14] are solved. Another advantage is the differential sensing principle, which is robust against background magnetic fields.…”

Inaccuracies of Giant Magneto-Resistive Angle Sensors Due to Assembly Tolerances

“…One particularly promising system uses GMRs integrated in a standard CMOS process (iGMR) [9]. All these sensors suffer from offset, gain mismatch, nonorthogonality, nonlinearity, cross-talk, hysteresis, and packaging effects [10], [11]. However, theses sources of errors can be largely suppressed by an individual multitemperature calibration at the end of the production line of the semiconductor manufacturer.…”

Compensation of the Piezo-Hall Effect in Integrated Hall Sensors on (100)-Si

“…With the advent of analogue CMOS technologies, it became possible to implement the long known spinning current principle [1], which reduces the Hall probe offset by two to three orders in magnitude [2], [3]. Another major step forward was the integration of memories into these analogue technologies, which are programmable after the die has been assembled in its package.…”