This paper presents a switched-capacitor Sigma-Delta modulator designed in 90-nm CMOS technology, operating at 1.2-V supply voltage. The modulator targets healthcare and medical diagnostic applications where the readout of small-bandwidth signals is required. The design of the proposed A/D converter was optimized to achieve the minimum power consumption and area. A remarkable performance improvement is obtained through the integration of a low-noise amplifier with modified Miller compensation and rail-to-rail output stage. The manuscript also presents a set of design equations, from the small-signal analysis of the amplifier, for an easy design of the modulator in different technology nodes. The Sigma-Delta converter achieves a measured 96-dB dynamic range, over a 250-Hz signal bandwidth, with an oversampling ratio of 500. The power consumption is 30 μW, with a silicon area of 0.39 mm².

The paper describes the design and implementation of power management circuits for RF energy harvesters suitable for integration in wireless sensor nodes. In particular, we report the power management circuits used to provide the voltage supply of an integrated temperature sensor with analog-to-digital converter. A DC-DC boost converter is used to transfer efficiently the energy harvested from a generic radio-frequency rectifier into a charge reservoir, whereas a linear regulator scales the voltage supply to a suitable value for a sensing and conversion circuit. Implemented in a 65 nm CMOS technology, the power management system achieves a measured overall efficiency of 20%, with an available power of 4.5 $\mathsf{\mu }$W at the DC-DC converter input. The system can sustain a temperature measurement rate of one sample/s with an RF input power of −28 dBm, making it compatible with the power levels available in generic outdoor environments.

This paper proposes a novel architecture for the generation of a programmable voltage reference: the background-calibrated (BC)-PVR. Our mixed-signal architecture periodically calibrates a static ultra low-power voltage reference generator, from an accurate bandgap reference. The portion of the chip used for the calibration can be powered down with a programmable duty-cycle. The system aims to fully exploit the small temperature derivative vs time $D_{T}$ of several application domains to minimize the average current consumption. The BC-PVR has been designed and implemented in TSMC 55-nm CMOS technology, and it achieves the largest reported programming reference output range [0.42 - 2.52] V, over the temperature range [−20, 85] °C. The duty-cycle mode allows nanoampere current consumption, and the large design flexibility permits to optimize the system performance for the specific application. These features make the BC-PVR very well-suited for power-constrained electronic systems.

This paper introduces a flexible multi-channel platform designed for integrating multiple sensors, among which electronic noses (e-nose) and electronic tongues (e-tongue), targeting food quality and safety assessments. The proposed device is designed aiming for maximum portability, allowing on-site analyses, and maximum modularity, to meet user requirements. The customizable configurations allow the user to adjust the number of channels, current ranges, and voltage settings and to perform different analyses simultaneously. A variable number of sensing modules with different features can simultaneously be interfaced with the same control board, equipped with a microcontroller unit and a wireless module to both process data for on-board analyses and send it to the cloud. The modular design of the system allows for interchangeable sensing modules, offering high flexibility in sensory analysis compared to the existing portable solutions. Two custom dual-channel module boards have been designed with different operating current ranges, minimizing power consumption for extended portability, requiring only 3.16mA per channel during operations of the high-current module and 2.11mA for the low-current module. Device characterization demonstrates high linearity, with an R-squared higher than 0.999 over the entire voltage range. The channel-to-channel gain mismatch is limited to 0.26%. Spectral analysis shows 20 μVrms of equivalent noise, leading to an equivalent minimum sensor resolution of 16 noise-free bits.