Frame Rate Improvement for Two-Dimensional Integrated Magnetic Sensor

Abstract

To improve the frame rate of a two-dimensional integrated magnetic sensor, the pixel structure and readout circuits were re-examined. The frame rate was improved by reducing the noise of the horizontal shift register by lowering the drive frequency and parallel reading (with 16 channels). With this idea, two-dimensional integrated magnetic sensors were designed and fabricated with the standard 0.35 μm CMOS process on silicon. The type of Hall sensor is n-type Hall sensor that uses an inversion layer under the gate oxide of the MOSFET. The Hall sensors were arrayed (64×64), and the control digital circuits and output amplifier were also integrated into the same chip. “One pixel” was 50×50 μm, and the entire chip was 4.9×4.9 mm. The frame rate was 7813 frames/sec at a 2-MHz horizontal shift register frequency. The average sensitivity of these sensors was 72.9 mV/(mA·T). The two-dimensional magnetic flux distribution was measured with a 3000-rpm, 1-mm-diameter Nd-Fe-B rare-earth permanent rotating magnet without image lag. From the measurement results, a high frame-rate magnetic sensor for motor control was successfully fabicated.