Study of First-Order Thermal Sigma-Delta Architecture for Convective Accelerometers

This paper presents the study of an original closed-loop conditioning approach for fully-integrated convective inertial sensors. The method is applied to an accelerometer manufactured on a standard CMOS technology using an auto-aligned bulk etching step. Using the thermal behavior of the sensor as a summing function, a first order sigma-delta modulator is built. This "electro-physical" modulator realizes an analog-to-digital conversion of the signal. Besides the feedback scheme should improve the sensor performance.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

High Resolution Micro-Pirani Pressure Sensor Gauge with Transient Response Processing

International audienceA micro-Pirani pressure sensor which acts as a pressure dependent thermo-resistance gauge is traditionally exploited using a steady state resistance measurement. However any signal variation occurs over a constant voltage bias due to the initial resistance of the device which affects the sensor's sensitivity. Our work shows for the first time an experimental investigation of a micro-Pirani gauge based on its dynamical behavior when heated by a current step. Such a processing does magnify the pressure dependence of the gauge's signal in eliminating the initial resistance influences on the measurement. Furthermore, a first order low pass filter step response identification of the experimental transient signal strongly reduces the thermal noise influence on the measurement. The heating step, the recording of the time dependent signal and its post-processing can be easily achieved by a small-size controller. The proposed system provides a substantial enhancement of the micro-Pirani pressure sensor performance

High Resolution Micro-Pirani Pressure Sensor with Transient Response Processing and Time-Constant Evaluation

International audienceA micro-Pirani pressure sensor, which consists of a pressure-dependent thermoresistance gauge, is traditionally exploited using a steady-state resistance measurement. Any signal variation occurs over an offset voltage due to the imperfection of the device, which affects the sensor's sensitivity. This paper presents, for the first time, an experimental investigation of a micro-Pirani gauge based on its dynamic behavior when heated by a current step. Such processing magnifies the pressure dependence of the gauge's signal by eliminating the constant offset influences on the measurement. Furthermore, a first-order low-pass filter step response identification of the experimental transient signal strongly reduces the noise influence on the measurement. Furthermore, such identification enables a direct calculation of the time constant. This paper investigates the pressure measurement based on the time-constant evaluation, which provides a range of measurement and a maximal sensitivity significantly shifted toward the atmospheric pressure compared to that of a traditionally processed Pirani gauge. The heating step, the recording of the transient response signal, and its digital postprocessing can be easily achieved by a small-sized controller. The proposed system provides a substantial performance enhancement of the micro-Pirani pressure sensor

Etude et réalisation de microcapteurs thermiques (anémomètre et accéléromètre thermique)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

A Comparative Study of Conditioning Architectures for Convective Accelerometers

International audienceIn this paper, we compare three different conditioning and readout electronics for CMOS convective accelerometers. The work is based on both characterization results and high-level simulations. The three following architectures are evaluated: (i) a simple amplifier, (ii) a chopper stabilized amplifier, and (iii) an innovative 1st-order thermal sigma-delta modulator. Experimental data are obtained using the hybrid combination of a 0.8µm CMOS integrated sensor and discrete electronics. Behavioral simulations were carried-out under Matlab®/Simulink® using small-signal models. The sensor model includes performance-limiting thermal phenomena and 1/f noise contributions. Previous studies describing the modeling of thermal sigma-delta modulators do not address device noise modeling, since most of the time, the performance of those modulators are limited by quantization noise. In our case, we show that the performance is limited by both the noise in the devices and the quantization noise

Noise Analysis of a First-Order Thermal Sigma-Delta Architecture for Convective Accelerometers

International audienceThis paper presents the study of an original closed-loop conditioning approach for fully-integrated convective inertial sensors. The method is applied to an accelerometer manufactured on a standard CMOS technology using an auto-aligned bulk etching step. Using the thermal properties of the sensor, a first order sigma-delta modulator is built. This “electro-physical” modulator realizes an analog-to-digital conversion of the acceleration signal. Besides, the feedback mode of operation improves the sensor overall performance

Design-for-manufacturability of MEMS convective accelerometers through adaptive electrical calibration strategy

International audienceIn this paper, we explore the use of an adaptive electrical calibration strategy in the context of design-for-manufacturing for MEMS convective accelerometers. The calibration principle relies on the adjustment of the heater power level such that sensitivity is set to a given target value. The idea is to define multiple sensitivity targets in order to improve production yield and to insert a criterion on power consumption. Different device binning can then be achieved depending on test limit settings. Results obtained from Monte-Carlo simulation are presented to demonstrate potentialities of the technique

Study of an electrical setup for capacitive MEMS accelerometers test and calibration

International audienceThis paper deals with the development of a fully electrical method to estimate the sensitivity of capacitive MEMS accelerometers in batch fabrication. The objectives are to test and calibrate them without the need of costly and time-consuming mechanical test equipments. Alternate electrical test measurements are introduced and two methods are evaluated. The first one is based on the analytical study of the relations between the electrical test parameters and the sensitivity. The second one is based on a regression analysis of these relations on a learning batch of sensors. Both are evaluated on a case study accelerometer with Monte Carlo simulations. Applying the methods for calibration shows that the dispersion of the sensitivity can be improved. Results show that the second method is more promising

Post-fabrication soft trimming of resistive sensors

International audienceA compact and efficient architecture is introduced as an alternative to laser-trimmed precision thin-film resistor. The purpose is to compensate for process-induced offset in Wheatstone bridges and to avoid the then-obtained degradation in terms of full-scale, non-linearity, power supply noise rejection... Expected advantages are a reduced cost due to the fully-electrical implementation and, depending on the programming technology, a possible re-calibration of high-end sensors

A Closed-Loop Architecture with Digital Output for Convective Accelerometers

International audienc