M. Ferri

Wearable wireless accelerometer with embedded fall-detection logic for multi-sensor ambient assisted living applications

In this paper we present a wearable wireless accelerometer device for people fall detection in ambient assisted living (AAL) applications, communicating with care holders and relatives of the assisted person through an ADSL based gateway. The wearable system is a PCB with a commercial three-axes, digital-output MEMS accelerometer chip, a ZigBee transceiver and a programmable logic (FPGA). The raw acceleration stream from the MEMS sensor is processed by suitable algorithms on the FPGA, whose aim is to detect potential falls and their level of confidence, delivering an alarm information to the gateway by means of the ZigBee transceiver. Several sessions of data collection with real actors have been performed to define and characterize fall detection algorithms. Experimental results show that the accelerometer is a fundamental component of a multi-sensor network system and on this basis a custom device has been realized.

Integrated micro-solar cell structures for harvesting supplied microsystems in 0.35-µm CMOS technology

In this paper we present a solar harvester test chip, realized to characterize several integrated solar cell structures, gathering the information required to design a complete power management system for handling the harvested energy. In particular, we realized photodiodes with three different geometries of the p-diffusion, and three different dimensions of the n-well. The chip is realized in a 0.35-µm CMOS technology, and the diodes feature different active area density, depending on the geometry of the p-diffusions. In order to evaluate the harvesting performance of the solar cells in real applications, we developed an equivalent circuit of the devices, based on the experimental data and we used it to design a power management system specific for discrete-time applications. The power management system is being integrated on the same chip of the micro solar cells, in a 0.35-µm CMOS technology.

An integrated system for people fall-detection with data fusion capabilities based on 3D ToF camera and wireless accelerometer

This paper presents a multi-sensor system for the detection of people falls in the home environment. Two kinds of devices are used: a MEMS wearable wireless accelerometer with onboard fall detection algorithms and a 3D Time-of-Flight camera. An embedded computing system receives the possible fall alarm data from the two sub-sensory systems and their associated level of confidence. The computing module hosts a data fusion software to operate the validation and correlation among the two subsystems delivered data in order to rise overall system efficiency performance with respect to each single sensor sub-system.

Integrated stabilized photovoltaic energy harvester

In this paper a photovoltaic power generator is presented. The energy harvesting device exploits the power generated by several on-chip micro-photovoltaic cells, connected in series, to provide the supply voltage and the reference voltages for an integrated voltage regulator. The regulator operates also with low illumination levels or large load currents, and tolerates a wide variation of the voltage produced by the micro-photovoltaic cell chain. In order to allow the series connection of several photovoltaic cells, we used an SOI technology, where parasitic p-n junctions to the substrate are not present.

Model of integrated micro photovoltaic cell structures for harvesting supplied microsystems in 0.35-µm CMOS technology

In this paper we present a micro photovoltaic cell model, validated by the experimental results obtained from a test chip realized in 0.35-µm CMOS technology. In particular, we analyzed and modeled the behavior of an integrated p-n junction when irradiated with incident light with solar spectrum, considering the parameters of a conventional 0.35-µm CMOS technology. We considered the effect of irradiation on the basic diode equation, which allows the estimation of the carrier photo-generation as a function of the geometrical parameters of the micro photovoltaic cell. This model is particularly useful to predict the available harvested power that can be delivered to an on-chip integrated microsystem. Based on the proposed model, we also developed an equivalent circuit of the micro photovoltaic cells, that can be used with circuit simulators to evaluate the performance of complete microsystems. The test chip realized to validate the model consists of a set of different integrated micro photovoltaic cells.

A 12.4 ENOB Incremental A/D Converter for High-Linearity Sensors Read-Out Applications

In this paper a 13b incremental A/D converter for high-linearity sensors read-out applications is described and characterized. The incremental solution is preferred to traditional SigmaDelta architectures to simplify the decimator filter topology, which is actually a single bit digital accumulator. This leads to lower area occupancy and power consumption. The input signal, which can be connected either in single-ended or differential mode, is sampled by a resettable SC integrator, followed by a discrete time comparator, which selects the feedback signal. The silicon prototype has been designed in 0.35mum technology with a power supply of 3.3V and consumes 950muW with throughput rate of 120Hz. The measurements results show an ENOB of 12.41 bits. The chip area is 0.22mm2.

A CMOS 2D Micro-Fluxgate Earth Magnetic Field Sensor with Digital Output

A complete CMOS integrated microsystem for detecting the direction of the Earths magnetic field (whose full-scale value is on the order of 60muT), realized with the micromodule approach, including both sensor and electronic interface circuit, achieves 4deg accuracy on the measured angle and provides a digital output. The system response is linear in the range of plusmn60muT with a maximum non-linearity error of about 3% of full-scale.

Photovoltaic Energy Harvester with Power Management System

We present a photovoltaic energy harvester, realized in 0.35-μm CMOS technology. The proposed system collects light energy from the environment, by means of 2-mm2 on-chip integrated microsolar cells, and accumulates it in an external capacitor. While the capacitor is charging, the load is disconnected. When the energy in the external capacitor is enough to operate the load for a predefined time slot, the load is connected to the capacitor by a power management circuit. The choice of the value of the capacitance determines the operating time slot for the load. The proposed solution is suitable for discrete-time-regime applications, such as sensor network nodes, or, in general, systems that require power supply periodically for short time slots. The power management circuit includes a charge pump, a comparator, a level shifter, and a linear voltage regulator. The whole system has been extensively simulated, integrated, and experimentally characterized.

A 0.35μm CMOS Solar energy scavenger with power storage management system

In this paper we present an integrated solar energy scavenger realized in a 0.35 μm CMOS technology. The proposed system collects solar energy from the environment through integrated diodes, accumulates it and, delivers it to the load when it is enough to allow proper operation of the CMOS circuitry. The proposed system is suitable for discrete-time regime applications, such as sensor network nodes or, generally, systems that require power supply periodically for short time slots. In order to properly design the system, we developed a model of the integrated solar cell on the basis of measurement data extracted from a test chip. The power management circuit, including a charge pump a comparator and a linear voltage regulator, has been extensively simulated.

Power Management Systems for Photovoltaic Energy Harvesters

In this chapter we present two different solutions of integrated photovoltaic energy harvesting, realized for discrete and continuous time working systems. The first solution is realized in a standard 0.35 ?m CMOS technology: it collects light energy from the environment, by means of 2 mm2 on-chip integrated micro-solar cells, and accumulates it in an external capacitor. While the capacitor is charging, the load is disconnected. When the energy in the external capacitor is enough to operate the load for a predefined time-slot, the load is connected to the capacitor by a power management circuit. The second solution is realized in 0.35 ?m SOI CMOS technology. The energy harvesting elements consist of 35 trench-insulated p–n junctions, while the sensing system consists of a bandgap reference circuit, including an integrated high precision temperature sensor, and a high voltage low drop-out voltage regulator.