High-speed CMOS magnetic angle sensor based on miniaturized circular vertical Hall devices
We present a high-speed CMOS integrated magnetic angle sensor consisting of two 8-contact circular vertical Hall devices (CVHD). The biasing and sensing of the Hall voltage is rotated clockwise for the first device, and counter clockwise for the second one. The output voltages of the two devices are processed separately in two channels and they act as a reference signal one to another. The output of the sensor is a pulse width modulated signal whose width is proportional to twice the angle enclosed between the in-plane magnetic induction vector and the reference axis. The information on the angle is directly present in the pulse width modulated signal without the need for either arctg function implementation or complicated angle detection algorithms. The sensor's concept together with optimized interface and signal conditioning electronics allows for very high bandwidth. The measurement range of the sensor is 0-90 degrees, with possibility for further extension. The sensor achieves tracking the angle of the in-plane magnetic vector oscillating at up to 200 kHz (12,000,000 rpm), or equivalently, having an angular speed of 628,000 tad/s. To our knowledge, this is the highest bandwidth of a completely CMOS integrated magnetic angle sensor. The maximum absolute error for these speeds is +/- 4 degrees without any calibration, the response time is 1 mu s, and the angular resolution is 0.5 degrees. (C) 2012 Elsevier B.V. All rights reserved.