Linearizing Relaxation-Oscillator Based Front-End for Magneto-Resistive Angle Sensors

This paper presents a new linearizing digital front-end for magneto-resistive (MR) angle sensor having sine and/or cosine transfer-characteristics. The front-end processes a dual half-bridge MR sensor and then outputs a linear indication of the sensing angle. It combines a simple relaxation-oscillator-based circuit with linearizing ratiometric technique to achieve the aforementioned task. The front-end provides several positive features such as (1) no requirement of precision and matched bipolar reference voltages, (2) simplicity of architecture, (3) independence from various circuit non-idealities. A detailed account of the proposed front-end is discussed with the help of systematic mathematical derivation. The performance of the front-end is verified with help of simulation as well as experimental studies and reported in this paper.