S.A. Bota

A reusable smart interface for gas sensor resistance measurement

The advances of the semiconductor industry enable microelectromechanical systems sensors, signal conditioning logic and network access to be integrated into a smart sensor node. In this framework, a mixed-mode interface circuit for monolithically integrated gas sensor arrays was developed with high-level design techniques. This interface system includes analog electronics for inspection of up to four sensor arrays and digital logic for smart control and data communication. Although different design methodologies were used in the conception of the complete circuit, high-level synthesis tools and methodologies were crucial in speeding up the whole design cycle, enhancing reusability for future applications and producing a flexible and robust component.

A current-mode interface circuit for a piezoresistive pressure sensor

An interfacing circuit for piezoresistive pressure sensors based on CMOS current conveyors is presented. The main advantages of the proposed interfacing circuit include the use of a single piezoresistor, the capability of offset compensation, and a versatile current-mode configuration, with current output and current or voltage input. Experimental tests confirm linear relation of output voltage versus piezoresistance variation.

A Monolithic Interface Circuit for Gas Sensor Arrays: Control and Measurement

The electronics for monolithically integrated gas sensor arrays fabricated using a compatible CMOS process have been developed. Circuitry includes the heater driver for temperature control and an interface circuit for inspection of the four sensors in the array. The operating temperature of the sensing resistors is between 200° and 400°C. The proposed temperature controller is capable of regulating the temperature of a 2100 × 2100 μm hotplate up to 400°C with a resolution of 2°C with 5 V supply voltage. A readout circuit based on a ring-oscillator has been included to measure the sensing resistance change upon gas exposure over a high dynamic range. Because it is robust, small, low priced and offers future capabilities with adequate signal processing, the system would be able to cover most of todays gas sensor markets.

Smart Power Integrated Circuit for a Piezoelectric Miniature Robot

A BCD technology (Bipolar, CMOS, DMOS) is used to implement a high voltage smart power integrated circuit in order to obtain a fully integrated Smart Powered Piezoactuator Unit (SPU) for a new generation of miniature robots with sizes around 1 cm3. The integrated circuit is based on a mixed-mode circuit with power analogue output circuitry and digital input control circuitry. A specific driving system strategy is defined based on ICs assembled on-board with a serial communication interface. This minimizes the number of wires connecting the miniature robot to improve the robot motion performances and is a first step towards fully autonomy. Six samples of the ICs have been assembled onto a driving platform and tested with good results.

A CMOS monolithically integrated gas sensor array with electronics for temperature control and signal interfacing

A monolithically integrated gas sensor array with conventional CMOS electronics has been developed. Circuitry includes the heater driver for the temperature control and the signal interface electronics for inspection of the four sensors in the array. Because of its characteristics as robustness, small, size, low price and future capabilities with the adequate signal processing the system would be able to cover most of todays markets considered for gas sensors.

Monolithic integrated magnetic sensor in a digital CMOS technology using a switched current interface system

A magnetic field-to-voltage converter using a magnetic MOSFET (MAGFET) device has been designed, simulated and tested. The sensor was measured under magnetic fields ranging from 0 to 0.8 T and the obtained sensitivity was 0.03 T/sup 1/ with an offset value lower than 0.2%. A macro model for the MAGFET in the saturation region is presented. Also, we have designed a complete integrated measurement system including the sensor, bias interface circuit and a A/D converter based on a current-mode technique.

Modelling, Design and Test of a Monolithic Integrated Magnetic Sensor in a Digital CMOS Technology Using a Switched Current Interface System

A magnetic field-to-voltage converter using a magnetic MOSFET (MAGFET) device has been designed, simulated and tested. The resulting sensor was measured under magnetic fields ranging from 0 to 0.8 T, the obtained sensitivity was 0.03 T-1 with an offset lower than 0.2%. SPICE macro model for the MAGFET in the saturation region is presented. Using an analogue Hardware Description Language (HDL-A) we have simulated the behaviour of the MAGFET and an interface circuit based on a custom current-mode sigma delta modulator.

A MOSFET-only second order delta-sigma modulator for capacitive sensor interfaces

A 14-bit MOSFET-only 2/sup nd/ order /spl Delta/-/spl Sigma/ modulator has been implemented in a 0.7 /spl mu/m CMOS process for capacitive sensors interfaces. A switched capacitor architecture that allows the substitution of linear capacitors by MOS capacitors has been developed. These circuits have low cost fabrication, small area, and high matching. This proposal was tested comparing two different /spl Delta/-/spl Sigma/ modulators, one with linear capacitors and the MOS-only version. Similar results were obtained for both modulators.

Force-balance interface circuit based on floating MOSFET capacitors for micro-machined capacitive accelerometers

The feasibility of a force-balance interface based on a second-order delta-sigma (/spl Delta//spl Sigma/) modulator for capacitive sensors has been analyzed in order to delimit the requirements to assure system stability for a given set of constraints related to the sensor-modulator system. A /spl Delta//spl Sigma/ modulator based on a switched-capacitor architecture with floating MOSFET capacitors has been implemented using a 0.7-/spl mu/m CMOS process. Nonlinear effects related to voltage dependence of the floating MOSFET capacitors have been avoided using a modulator architecture based on charge integrators. The behavior of the new proposed modulator has been measured experimentally and compared with an equivalent interface made with lineal capacitors. Similar results were obtained from both systems. In both circuits, the modulator resolution was better than 14 bits at a sample frequency of 250 kHz, and oversampling ratio of 256.

A mixed-mode circuit for interface control and gas sensor resistance measurement

3- AM - A mired-mode interface circuit for monolithically integrated gas sensor arrays has been developed Circuiity includes interface electronics for inspection of up to four sensors array and interface logic for sman control. Because of its characteristics (IS robustness. small, size, low price and future capabilities with the adequate signal processing the system composed by the sensor and the application specific integrated circuit would be able to cover most of today markets considered for gas sensors.