Offset reduction in a multiple-terminal hall plate using current spinning

Abstract

The present work analyzes a four-terminal Hall-plate device to determine the main sources of error and explain how current-spinning technique can be used to effectively reduce offset and noise. Based on this analysis, an improved magnetic sensor is designed using an eight terminal octagonal Hall plate and a chopped-based control circuit to implement the current-spinning technique. Since Hall plates are complete compatible with the CMOS manufacturing process, a monolithic chip which contains the sensor, switches, digital control and bias circuit were fabricated using a 0.6 μm commercial CMOS process. These devices are used to test the offset cancellation methodology and compare if there are advantages related to the device orientation or switching sequence. Experimental results show a residual offset of 0.25 mT, a 99% reduction compared with the original offset level measured at Hall plate.