A Novel Linearizing Signal Conditioner for Half-Bridge Based TMR Angle Sensor

Abstract

This paper proposes a novel signal conditioning circuit for half-bridge topology based Tunneling Magneto-Resistance (TMR) angle sensor. The resistances of TMR angle sensor vary as a sine/cosine function of the shaft angle. The proposed circuit employs an enhanced dual-slope technique to process these non-linear resistance variations and render a linear digital output for full-circle range. The circuit uses easily available and low-cost circuit components, and a novel linearization logic in its architecture. It possesses low dependence on many circuit and sensor non-idealities. Further, a novel algorithm is proposed to reduce the measurement error due the mismatch in nominal resistances of the TMR sensor. The working of the circuit is verified using simulation as well as experimental studies. The maximum non-linearity in the circuit output, observed with expected sine/cosine characteristic, is 0.038 %. Later, a shaft angle sensing unit, employing AAT003-10E half-bridge TMR angle sensor IC, is designed, built, and characterized. The interfacing studies showcase the capability of the developed signal conditioning circuit for linearizing practical TMR angle sensors. The efficacy of the compensation algorithm is also proved in the experimentation.