A 200μW Eddy Current Displacement Sensor with 6.7nmRMS Resolution
Matheus Ferreira Pimenta (Cypress Semiconductor, Cork, Student TU Delft)
Cagri Gürleyük (TU Delft - Electronic Instrumentation)
Paul Walsh (Cypress Semiconductor, Cork)
Daniel O’Keeffe (Cypress Semiconductor, Cork)
M Babaie (TU Delft - Electronics)
Kofi A.A. Makinwa (TU Delft - Microelectronics)
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Abstract
This paper describes a low-power eddy current displacement sensor intended for safety-critical touch applications. A sensing inductor is incorporated into a digital PLL to efficiently digitize the displacement of a flexible metal foil. At a stand-off distance of 500μm, the sensor achieves 6.7nm resolution in a 3kHz bandwidth over a 43μm range. It consumes 200μW from a 1.8V supply, which represents a 35× improvement on the state of the art.