Modern power electronics applications demand compact and low-power magnetic field sensors with increased bandwidth performance. In this perspective, current-mode readout topologies of magnetic sensors based on a transimpedance amplifier (TIA) were recently proven to be effective solutions. This paper gives an insight into TIA design trade-offs with a specific focus on their application to the readout of magnetic field sensors. Based on this review, the paper details the microelectronic circuit design of a resistive-feedback TIA (R-TIA) specifically tailored for bridge-based resistive magnetic sensors and discusses trade-offs between noise, power, and bandwidth performance. The proposed architecture is fully differential and self-biased, and is implemented in a 90-nm microelectronic process from STMicroelectronics. The developed R-TIA achieves up to 45 MHz bandwidth with a 1.2-V supply, in simulation. Experimental tests of the proposed R-TIA as a current-mode readout for an integrated Hall-effect magnetic sensor are also reported with input signals in the MHz range, proving the suitability of R-TIA for the readout of broadband magnetic sensors.

A Threshold Voltage Generator (TVG) circuit for continuous-time comparators is presented. It may be used in ULP IoT systems requiring nanoWatt power consumption, kbps bitrates and the reception of packets with lengths up to hundreds of bits. The circuit is based on a switched capacitor technique to generate the threshold voltage without requiring any large area resistors and with the system clock active only during the reception of data, thus minimizing energy consumption. Latency is also minimized as the threshold is generated within the first received bit of the packet. The reception of packets with no limits on their length is made possible by continuously updating the threshold, which also allows correct operation even in case of amplitude variations in the incoming signal during the data reception. It has been implemented and verified through post-layout simulations in an STMicroelectronics 90-nm CMOS technology with a 0.6-V supply, targeting a 1-kbps bitrate. It occupies an area lower than 0.001 mm2, which is less than 1% of the area of a standard RC-based TVG implemented in the same technology. A prototype of the proposed TVG is currently under fabrication.

The paper focuses on an electronic interface which can be used into piezoelectric energy scavenging systems (PESS). These systems convert the energy of mechanical vibrations into electrical energy using a piezoelectric transducer to realize a power supply for low power electronic systems. To obtain a suitable supply source an AC-DC conversion of the output signal of these transducers is needed and, since the output power level of the energy scavenger can be very low, the conversion should be as efficient as possible. This paper shows an active voltage doubler AC-DC converter for PESSs. A novel driving circuitry topology is presented; it has the advantage to be tolerant with respect to the process variations. The converter uses exclusively a fraction of the harvested energy to supply itself and a bias circuit has been designed to make the total current consumption supply independent. The simulation results show that the efficiency of the AC-DC converter can be as high as 94%. The circuit will be diffused in 0.35 mum CMOS STMicroelectronics technology.

In recent years a lot of studies focused on Energy-Scavenging Systems (ESS). An important motivation for these studies is the development of Portable Devices (PD) and of Wireless Sensor Networks (WSN). An ESS can be partitioned in two sections: the energy-scavenger itself and the electronic interface. The first one is the energy transducer while the second one is the electronic circuit which manages the energy. One of the most important objectives of the electronic interface is to realize the required ac-dc conversion. Since the output power level of the energy-scavenger can be very low, the conversion should be as efficient as possible. The goal of this paper is to design an active, high efficiency voltage doubler ac-dc converter for piezoelectric ESS which exclusively uses a fraction of the harvested energy to supply its active devices. The circuit was diffused in 0.35μm BCD6s technology. The simulation results show that it is possible to obtain a maximum efficiency of the ac-dc converter equal to 91%. Premiliminary experimental measurements were performed and the results obtained are in good agreement with simulations.