A linearizing interface circuit with phase-error compensated direct-digital output for TMR-based angular position sensor

This paper proposes a simple and efficient electronic interface circuit for Tunneling Magneto-Resistance (TMR) based angular position sensor. The proposed circuit takes-in and processes the sine and cosine natured outputs of a TMR angle sensor using a novel methodology, and provides a linear output with angle for a full-circle range. The new methodology ensures that output has minimal dependence on phase-error of the oscillator employed in the circuit. The scheme also provides a digital output without using any separate analog-to-digital converters. Mathematical explanation of the proposed methodology and the interface circuit is presented. The basic working of the scheme is ascertained using simulation and emulation studies. The results show that the scheme has excellent output-linearity and very low dependence on the phase-error. Further, the circuit is tested with a prototype TMR angular position sensor unit. The overall system gave a low and nearly-constant non-linearity of around 0.55 % for different phase errors. Finally, comparison studies to show that the developed scheme offers better performance when compared with an existing high-performing scheme.