The ams OSRAM patented principle uses four on-chip Hall sensors arranged in a circle to provide the angle information as sine and cosine. The signals generated by the Hall sensors are amplified, converted to digital and then filtered to suppress the noise. The embedded CORDIC  algorithm calculates the angle and the magnitude of the magnetic vector. An Automatic Gain Control (AGC)  works in closed loop to compensate to temperature, magnet strength and environmental variations as change of air gap, for example.