Abstract
We present a new Hall sensor design for the accurate and robust measurement of linear displacement. Implemented in CMOS, the sensor is based on a novel gradient measurement concept combining Hall elements with integrated magnetic concentrators. In typical applications with practical Ferrite magnets, the peak output voltage of the Hall transducers is only around 1.7 mV at the maximum operating temperature of 160°C, and thus requires high-performance low-offset readout electronics. Over its 15-mm linear displacement range, the sensor’s total error is 1% including manufacturing tolerances, trimming accuracy, temperature, aging effects, and practical magnet constraints. In addition, the sensor is immune to magnetic stray fields up to 5 mT, complying with the most stringent automotive norm.
Highlights
A BOUT 6 billions semiconductor magnetic sensors are shipped each year [1]
About 100 production samples were subjected to AEC-Q100 qualification tests to emulate the lifetime mission profile
The standard deviation of the residual offset after embedded software correction at 160 ◦C was below 5 μV
Summary
Magnetic sensors cover a range of technologies: Hall, AMR, GMR, TMR, magneto-inductive and others. They serve numerous applications such as compass, position (angle, linear displacement), and current sensing. For example in [2], magnetic fields of several hundreds of μT were measured in electric vehicles, and traced to traction currents. Such level of stray field would corrupt any accurate magnetic sensor measurement if left unmitigated. We focus here on compact linear displacement sensor with a full-stroke above 10 mm. This is by contrast to close proximity sensors where the full-scale range is limited to a few millimeters, but with sub-nanometer resolution [3]
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