Design and development of hall sensors for magnetic microsystems

Nowadays, magnetic sensors are widely used in variety of applications. One of the most common classes of magnetic sensors is Hall effect based sensors. Improving characteristics of Hall effect based sensors, such as sensitivity, resolution, power consumption, and chip area has always been a center of attention for many researchers. In this work, a Hall sensor is designed in 0:13m CMOS technology. Two cross-shaped Hall plates are used to increase sensitivity and to cancel the DC ofset output of Hall plates. To provide input current for the Hall plates, a biasing circuit is designed. Using a common mode feedback network, consistency of the input current is ensured. To automatically ignore the process variations, which causes asymmetric output from different Hall plate ports, the current spinning method is used. 32 switches are connected to input-output ports of the Hall plates to rotate their connections functionality and compensate the probable defects after fabrication. A digital circuit is designed to generate 4 non-overlapping clock signals to control the switches. In order to increase signal to noise ratio, the signal is converted from current to voltage mode using a capacitor and then amplified using two fully differential amplifiers. The capacitor is discharged every complete cycle to ensure linear functionality. Layouts of different blocks used in the project are designed and pre-layout and post-layout simulation results are gathered and presented. Simulation results show sensitivity of 8383 V/(A.mT) and power consumption of 36 uW, while using 3 uA as input bias current, 1.8 V as supply voltage, and consuming 6259 um2 of chip area.