Accurate sensor readout circuitry for reliability measurement of hermetically sealed chip-scale biomedical implants

With steady miniaturization of neuroprosthetic implants, testing the hermeticity of the device encapsulation requires unprecedented level of sensitivity. To this end, developing new sensors and associated readout circuitry has become an ineluctable part of research in this field. This paper presents the design of a readout scheme that is capable of interfacing with either resistive or capacitive sensors and performs signal processing based on `lock-in' technique to enhance the effective resolution. The design methodology focuses on low noise, high accuracy readout and adaptability to a wide range of baseline values and different sensitivity levels of various types of sensors. The circuit is being fabricated on 0.5μm Silicon-on-Sapphire process and experiment setup is currently being carried out.