A 10-mW two-channel fully integrated system-on-chip for eddy-current position sensing [in biomedical devices]

The use of magnetic bearings in small 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-a-chip (SOC) for two-dimensional (2-D) differential position sensing in magnetic bearings through two pairs of eddy current sensors. It consists of a 312.5 kHz switched-capacitor (SC) sine-wave generator, a two-channel data acquisition unit including a 19-dB quadruple difference instrumentation amplifier, and a demodulating 12-bit ΣΔ analog-to-digital (A/D) converter with DSP-compatible serial interface. A signal-to-noise-plus-distortion ratio (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 a 2.7-V supply