Carlos Azeredo Leme

Multi-purpose interface for sensor systems fabricated by CMOS technology with post-processing

Abstract We propose an interface design strategy for CMOS sensor systems. The objective is to provide a microprocessor compatible sensor on a single chip. Great flexibility and robustness are achieved by the use of a sigma-delta modulator in the A/D converter and by including the sensor element in the modulator first stage. Implementations for three different classes of sensors, namely, a magnetic, a humidity and a thermal sensor, are presented.

Low noise multirate SC read-out circuitry for thermoelectric integrated infrared sensors

In this paper we present a switched capacitor multirate read-out circuit for thermoelectric infrared sensors integrated on chip. The target application is a passive intrusion detector. The signal generated by the sensor in this particular application is quite small (few tens of /spl mu/V) and has a narrow bandwidth (0.1+10 Hz). It must be amplified (keeping the noise level as low as possible) and band pass filtered. An auto-zeroed low-noise transconductance stage transforms the sensor output voltage in a current, which is applied to a multirate switched capacitor integrator, performing the signal processing. A prototype was integrated in a 1.2 /spl mu/m CMOS technology. Simulation and experimental results are reported.<<ETX>>

Linear CMOS power controller for precision sensor applications

The authors describe the design and implementation of a controlled power source. Its function is to stabilize power over a reasonable range of load variations. A solution using only linear circuit blocks is proposed in order to avoid an analog multiplier. This is achieved by making the power regulation around the nominal operating point and keeping only the first order correcting terms in the compensation equation. The error introduced by this approach is smaller than 0.2% for 10% load variation, which gives a stabilization factor of 50. The circuit was integrated as a driver for the resistor heating element of an air flow sensor cointegrated on the same chip.<<ETX>>

Interfaces for Microsensor Systems

We propose interface design strategies for CMOS sensor systems. The objective is to provide a microprocessor compatible sensor on a single chip. The interest of noise-shaping and oversampling techniques providing great flexibility and robustness are demonstrated. A new architecture for an oversampled noise-shaping A/D converter is also presented. It allows a significant simplification of the on-chip circuits, at the expense of high-speed signal processing at a remote data acquisition site.

Programmable CMOS analog function synthesis

The design and implementation in CMOS of an analog function synthesis circuit is described. The circuit structure is highly modular and is composed of identical nonlinear cells, each producing a movable bumped amplitude characteristic. By programming the weight and position of the individual bumps, practically any memoryless and smooth nonlinear characteristic can be generated. This circuit has application in the calibration of sensor nonlinearities and in waveform shaping.<<ETX>>

An oversampled modulator for A/D conversion with minimized analog content

In this paper we present a new modulator architecture for A/D conversion. This modulator allows a great simplification of the analog front end at the expense of a more complex digital signal processing for the bit stream decoding. Moreover, the system can be partitioned into two blocks communicating through noise immune signal lines. These two features, are very advantageous for sensor interfaces in remote locations and where only a minimal amount of circuitry can be co-integrated with the sensor. Extensive computer simulations demonstrate the feasibility of this approach.<<ETX>>

Oversampled interface for IC sensors with minimized analog content

In this paper we present a new oversampled modulator architecture for A/D conversion. This modulator allows a great simplification of the analog-front-end circuits at the expense of a more complex digital signal processing for the bit stream decoding. Moreover, the system can be partitioned into two blocks communicating through noise-immune signal lines. These two features are very advantageous for sensor interfaces in remote locations and where only a minimal amount of circuitry can be cointegrated with the sensor. >

Switched capacitor dual-collector magnetotransistors

In this paper we propose new approach to operate Suppressed Sidewall Injection dual collector Magnetotransistor (SSIMT), which allows one to reduce the power consumption and to implement directly switched capacitor signal-processing functions. This is obtained using charge instead of current to drive the device. Because of the clocked operation, the static power dissipation is eliminated and a sampled signal is obtained directly from the sensor. The proposed approach has been experimentally verified and the obtained results are presented.<<ETX>>

Bipolar circuits for stabilization of power in variable resistors

The authors describe bipolar circuits designed to control and stabilize power dissipated in a variable load resistor. Three approaches are used. The circuits can be designed with two linear voltage-controlled current sources or with a controlled current source introduced in the translinear loop of four transistors or by using a translinear loop with two currents where the load power is controlled by two voltage and current external sources. The errors of power stabilization are compared.<<ETX>>