Performance Tradeoffs of Three Contactless Angle Detection Systems

Three novel integrated CMOS interfaces suited for magnetoresistive sensor bridges are described. The first ASIC is all-analog, being the simplest and cheapest one. The second ASIC is a mixed-mode solution providing a PWM output, and its main innovation is the use of a compact nonlinear ADC to compensate for the sensor nonlinearity. This way, linearization and A/D conversion are performed simultaneously, saving power and silicon area. The third ASIC is mostly digital and fully programmable, being the most flexible and accurate (albeit costly) solution. It incorporates as main novelties a new offset compensation technique that shares most of required circuits with the successive-approximation ADC, and a new combinational circuit for sensor linearization. Measurement results for the three sensor interfaces are provided, and their performance tradeoffs discussed.