Abstract
Pressure sensors are used in many applications in fields such as automotive, industry, defense, aeronautics, space and other harsh environments. If we put aside the capacitive detection sensors, they are essentially resistive sensors consisting of strain gauges for the purpose of detecting membrane deformation. These are piezo-resistive sensors that cover a wide range of pressures of several hundred bars. Whoever, the task becomes difficult for measuring pressure levels below 5 bars with larger and much more expensive sensors. Over the past decades, the needs for miniaturization, low power consumption, cost reduction and reliability have favored the development of smart sensors based on MEMS combining a high level of performance and a low manufacturing cost for large volumes. It is in this context that the objective of this thesis is positioned : to propose two innovative solutions for the conditioning of resistive sensors in general with applications identified for pressure sensors.The first solution proposed is an alternative of the adjustment, by LASER ablation,of a matrix of resistors intended to compensate for the post-manufacturing offset, toadjust the scale factor and to limit the temperature drifts of a Wheatstone bridge. To achieve this, we have proposed a compact and efficient integrated circuit architecture that can be encapsulated in the same box as the sensor while maintaining compatibility with a passive sensor based on a Wheatstone bridge in terms of operation as well as number and input-output type. The expected advantages are a reduced cost thanks to the purely electrical implementation and an extension of the lifetime of the sensor thanks to an offset compensation at each power-up or on demand throughout the lifetime of high sensors of range.The second solution is based on the design of a second-order Sigma Delta (Σ∆)modulator based on a Wheatstone bridge architecture with integrated amplifier andcurrent recycling, patented by the LIRMM. It makes it possible to obtain a digital output signal with much lower consumption and size than for a conventional architecture composed of a passive sensor, a signal amplification chain and an analog-digital converter while maintaining an equivalent level of performance. The demonstrator produced converts an analog signal of around 20mV, coming from a sensor, into digital, with a resolution of 0.008% ie more than 10,000 measurement points (>13 bit).