DESIGN AND VALIDATION OF ELECTRONIC SYSTEMS FOR SENSOR CONDITIONING

In the last few years the great advances in process technology has lead to a dramatic increase of the density of electronic functions, furthermore latest refinements in photolithography techniques has featured an increasing shrinking of dimension of sensing elements up to the development of the Micro Electro Mechanical Systems (MEMS) in which mechanical elements, sensors, actuators, and electronics are integrated on a common silicon substrate. This rapid development of integrated systems has had a strong impact on a wide range of applications whose field of interest is focussed on sensing, conditioning and actuating activity. If in the last decades the diffusion of measurement systems was limited by high costs, large size and low reliability, the new generations of MEMS sensors guarantee remarkable savings in cost, area and power consumption featuring a deep spreading of the possible application for such systems in various market fields. This thesis deals with the development of sensor systems mainly targeting the new generation of MEMS sensors, which achieves a great reduction of area and power consumption but on the other hand requires more complexity in the conditioning interface. This work also faces the emerging issues deriving by the increasing complexity of electronic interface tight with the constant reduction of time to market which forces companies to review the design flow to maintain a high level of product quality. This research is then providing new tools and methodologies to enhance the design phase from architectural space exploration to verification of the whole system, and joining pre-silicon simulations to post-silicon verification aiding testing of electronic systems which is close to become one of the major cost factor for ICs companies. The compound scenario concerning the development of sensor systems is presented in Chapter 1, together with an overview of sensor systems market with a particular focus on the latest MEMS technology devices, and related applications in various segments. Chapter 2 introduces the state of the art for sensor interfaces: the generic sensor interface concept (based on sharing the same electronics among similar applications achieving cost saving at the expense of area and performance loss); and the Platform Based Design methodology which overcomes the drawbacks of generic sensor interfaces by keeping the generality at the highest design layers and customizing the platform for a target sensor achieving optimized performances. An evolution of Platform Based Design achieved by implementation into silicon of the ISIF (Intelligent Sensor InterFace) platform is therefore presented. ISIF is a highly configurable mixed-signal chip which allows designers to perform an effective design space exploration and to evaluate directly on silicon the system performances avoiding the critical and time consuming analysis required by standard platform based approach. Chapter 3 describes a verification and validation methodology for complex mixed signal ICs. A VHDL-AMS system verification methodology allows designers to derive VHDL-AMS models from full-custom schematics through a semi-automatic approach (featuring modeling time reduction and coherency between models and schematics), obtaining a behavioral model of the whole analog section for top level system verifications. The verification environment has been also enhanced by an integrated flow to bridge pre-silicon simulation to post-silicon verification relieving time consuming procedures for testing the prototype and featuring automatic data exchange between design and test environments. In Chapter 4 an application of the ISIF platform for design and validation of a sensor system for measuring water flow based on a hot wire anemometer in MEMS technology is described. The ISIF approach and the tools developed in the proposed verification flow have featured a fast and accurate evaluation of the whole sensor system overcoming time consuming system simulations needed in traditional approaches for architectural exploration and bringing to light phenomena related to the sensor and the surrounding media of the tailored application hardly foreseeable at system level. In the last chapter we describe the design of a smart sensor interface for conditioning all resistive class of sensor to face the market demand for low cost, optimized, high performance sensor systems. The proposed interface combines high quality signal conditioning with low size and advanced low power techniques, embodying an optimal candidate for mass production. The architectural space evaluation and the application prototyping with ISIF has enabled an effective, rapid and low risk development of the interface achieving an optimized sensor system for water flow monitoring achieving the high performances obtained with ISIF with noteworthy savings on area, cost and power