Abstract
Integrated CMOS Hall sensors have been widely used to measure magnetic fields. However, they are difficult to work with in a low magnetic field environment due to their low sensitivity and large offset. This paper describes a highly sensitive digital Hall sensor fabricated in 0.18 μm high voltage CMOS technology for low field applications. The sensor consists of a switched cross-shaped Hall plate and a novel signal conditioner. It effectively eliminates offset and low frequency 1/f noise by applying a dynamic quadrature offset cancellation technique. The measured results show the optimal Hall plate achieves a high current related sensitivity of about 310 V/AT. The whole sensor has a remarkable ability to measure a minimum ±2 mT magnetic field and output a digital Hall signal in a wide temperature range from −40 °C to 120 °C.
Highlights
Hall magnetic field sensors are widely established for their great applications in industrial control systems, intelligent instruments, and consumer electronic products, etc
Since the 90° rotation symmetrical Hall plate can be considered as a distributed resistive Wheatstone bridge from a dc point of view, the dynamic offset cancellation can be achieved by the spinning current method [3,4]
A novel signal conditioner with a simple structure is proposed for saving chip area and improving the performance of the sensor
Summary
Hall magnetic field sensors are widely established for their great applications in industrial control systems, intelligent instruments, and consumer electronic products, etc. They are used for direct measurement of magnetic fields, and for non-direct measurements, like speed or position, etc. Integrated CMOS Hall sensors suffer from a lot of non-idealities [2,3,4] First of all, their magnetic field sensitivity is very low. A CMOS Hall device is very vulnerable to process fluctuation, temperature drift and package-induced stress These negative factors induce serious offset voltage and low frequency 1/f noise which may be large enough to obscure the Hall signal.
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