This paper presents a temperature-stable system for wide-bandwidth contactless current sensing. It employs a multi-path combination of Hall sensors (low frequencies) and coils (high frequencies) to sense the magnetic field produced by a current-carrying conductor under a chip. To cancel the effect of earth's common-mode field, a differential sensing arrangement is used. This is further exploited to stabilize the Hall sensor's temperature drift with the help of a self-generated AC common-mode field. In a test chip fabricated in a 0.18 µm CMOS process, the stabilization scheme reduces the Hall sensor's sensitivity drift from 22% to 1% from −45°C to 105°C, corresponding to a temperature coefficient of 76 ppm/°C. The complete system has a bandwidth of 3 MHz, which represents a 10x improvement on previous low-drift CMOS magnetic sensors.
['Junfeng Jiang', 'Kofi A. A. Makinwa']
A hybrid multi-path CMOS magnetic sensor with 76 ppm/°C sensitivity drift