A 10 mW 2-channel fully integrated system-on-chip for eddy-current position sensing

The use of magnetic bearings in small and biomedical devices poses new challenges for the integration of complex embedded electronic systems. This paper describes a low-power fully integrated two-channel system-on-chip (SOC) for two-dimensional (2D) differential position sensing in magnetic bearings through pairs of eddy current sensors. It consists of a switched capacitor (SC) 312.5 kHz sine-wave generator and a two-channel data acquisition unit including a 19 dB quadruple difference instrumentation amplifier, and a demodulating 12 bit ΣΔ modulator with on-chip decimation filter and DSP-compatible serial interface. A SNDR of more than 60 dB has been achieved which corresponds to a resolution of better than 3 µm at a maximum displacement range of 3 mm. The entire system has been integrated in a standard 0.6 µm CMOS technology and consumes 10 mW at 2.7 V supply.