Mixed signal interface circuitry for low power multisensor microsystems

Driven by advances in technology and high demand in many applications, integrated microsystems have become a very important next-generation field in the semiconductor industry. The rapid progress achieved in integrated circuits (IC) and micro-electro-mechanical systems (MEMS) has made it possible to combine transducers and microelectronics in a single substrate or small package. However, the development of ultra-miniature and low power multi-sensor microsystems still faces numerous obstacles, including many that can only be addressed by the implementation of novel mixed-signal circuit structures.;This dissertation explores the implementation of highly configurable, multi-parameter, sensor interface circuits, which are optimized for modular multisensor microsystems that can be adapted to a multitude of applications. A custom mixed-signal IC has been developed to read out a wide range of transducers and communicate with a microcontroller, fulfilling a key role in an integrated microsystem platform. The microsensor interface circuit integrates programmable analog circuits with a digital communication interface, allowing sensor signal selection, readout circuit configuration, and power management. The readout block supports multiple sensor signal modes, including digital, capacitive, resistive, voltage, and current, using highly programmable analog circuits that can be configured to match the range and sensitivity of a large variety of sensors. The interface chip supports several system-level features that are essential to next-generation integrated microsystems, including built-in self test and self calibration, power management, and expandability to future applications. Several implementations of the interface circuit have been developed, including a 2.2x2.2 mm2 CMOS chip that supports up to eight sensor inputs, provides gain and offset control through a communication bus and on-chip memory, and achieves good readout sensitivity (e.g., 30mV/fF and 18mV/O) with high resolution (e.g., <1fF at 10Hz bandwidth and better than 10O).;Due to the rapidly emerging capabilities of chip-scale electrochemical sensors, special emphasis was placed on the development of a high performance, highly adaptive, integrated potentiostat for single-chip electrochemical array microsystems. The fabricated CMOS circuit supports amperometric output from 10pA to 10muA to suit a range of transducers, achieves sub-pA resolution using a switched-capacitor current readout block, and supports advanced interrogation techniques such as cyclic voltammetry. Furthermore, a fully differential current sensing circuit with full offset compensation has been designed to cancel leakage inherent to high density electrode arrays. Combined with post-CMOS fabrication of electrodes on the surface of the chip, the CMOS potentiostat has proven fully functional for electrochemical measurements while immersed in an electrolytic solution.