Emerging data-intensive computation has driven the advanced packaging and vertical stacking of integrated circuits, for minimized latency and energy consumption. Yet a monolithic three-dimensional (3D) integrated structure with interleaved logic and high-density memory layers has been difficult to achieve due to challenges in managing the thermal budget. Here we experimentally demonstrate a monolithic 3D integration of atomically-thin molybdenum disulfide (MoS₂) transistors and 3D vertical resistive random-access memories (VRRAMs), with the MoS₂transistors stacked between the bottom-plane and top-plane VRRAMs. The whole fabrication process is integration-friendly (below 300 °C), and the measurement results confirm that the top-plane fabrication does not affect the bottom-plane devices. The MoS₂transistor can drive each layer of VRRAM into four resistance states. Circuit-level modeling of the monolithic 3D structure demonstrates smaller area, faster data transfer, and lower energy consumption than a planar memory. Such platform holds a high potential for energy-efficient 3D on-chip memory systems.

This paper presents a chip-scale ultralow quiescent current power management system that interfaces with electromechanical energy harvester for enabling self-powering, batteryless wireless sensors. A piezoelectric transducer scavenges and transforms mechanical vibration energy into electricity in ac form, which is then converted into dc power by a full bridge rectifier and collected into a small filter capacitor. A buck-boost converter, as an impedance matching converter to achieve maximum power point tracking, further transfers the energy into a supercapacitor, from which a low-dropout (LDO) regulator powers an on-chip CMOS sensor with clean power supply. Additionally, the energy stored in the supercapacitor can be used to drive a radio frequency transmitter. These components form a complete wireless sensor node, applicable for the Internet of Things sensor networks. The chip is fabricated by using a standard 0.5 μm CMOS process. From measurements we have verified all the key merits of this design: first, a high voltage converting efficiency (up to 97.1%) of the rectifier; second, a minimum of 102 s charging time to charge a 1 mF supercapacitor from 0 to 3.3 V of the buck-boost converter with impedance matching method; and third, a 10 nA to 100 μA load current range and at least 85° phase margin LDO regulator with ultralow quiescent bias current as low as 750 pA.

In this paper, a proof-of-concept high-efficiency rectifier-booster regulator (RBR) with an impedance matching converter operating at 2.45 GHz is proposed. An entire WLAN energy harvesting system is demonstrated. A flower-shaped broadband dual-polarized cross dipole antenna with a full-wave matching network is employed to harvest electromagnetic energy from a WiFi router. A novel RBR is proposed to rectify the RF energy to dc and boost the output voltage. It is evolved from a Greinacher rectifier and two Cockcroft-Walton charge pumps to form a full-wave rectifier. An equivalent resistance model is established to evaluate the optimal stage of the RBR. Furthermore, a boost converter is designed as an impedance matching converter to harvest as much energy as possible from the RBR and store the energy into a 1-mF supercapacitor. Experimental results show that the RBR can provide 1.7-V output voltage under -10-dBm input power. In addition, the RBR can achieve up to x 3.4 voltage boosting with 85% voltage conversion rate (VCR) and provide a higher than 1-V output voltage within a distance of 50 cm between an antenna with 20-dBm transmitting power and the rectenna. The excellent performance shows the wide practicality of the proposed design method for the Internet-of-Things (IoT) applications.

Wireless power transmission (WPT) system is widely used in implantable biomedical applications. Conventional power management unit (PMU) in the secondary side normally consists of rectifier and DC-DC converters in series, which shows low power conversion efficiency (PCE). In this work, we propose a single-stage AC-DC converter with dual regulated-outputs, combining output regulation with full-wave active rectifier, which not only improves the power efficiency, but also saves silicon area. Also, a new scheme of delay control is designed to eliminate the high-speed and high-precision comparator used in conventional rectifier, thus reduces the power loss significantly. Trough reusing MOS transistors and adjusting the gate voltage swings, 2X and 3X step-up regulated voltages are realized. A 13.56 MHz integrated AC-DC converter that delivers 10mA output power has been implemented in a standard 180nm CMOS process with a small chip area of 0.663mm². Measurement results demonstrate that it can properly operate with a 0.5~1V AC input, directly providing two regulated DC output voltages of 1.7V and 2.75V. Peak PCE of 79% is obtained under the load of 7.1mW. It has the benefits of compactness, high PCE, high voltage conversion ratio (VCR) and flexible outputs. To date, this work is the first to report the single-stage AC-DC converter with regulated multi-outputs for WPT systems.

Multiple loops have been used extensively to enhance the system performance in various applications. However, the increasing complexity of multi-loop systems also makes them much more difficult to analyze and implement. In this paper, a new methodology to analyze multi-loop system is proposed. In the proposed framework, multi-loop systems are regarded to be built upon of sub-modules of cascade, parallel adding, and feedback units, and then, they are simplified following a certain procedure based on the correlation of the Bode characteristics of the segmented sub-modules. Applying this methodology, the Bode plot and the transfer function of the system can be easily obtained with the system properties of gains, zeros, and poles. Two examples are provided as demonstrators, including a multi-loop low-dropout regulator (LDO) from literature, and a newly designed multi-loop LDO aiming at enhancing the stability over a wide load range, which show that the Bode plot and the transfer function can be obtained more intuitively and rapidly. Excellent agreements among theory, simulations, and measurements are confirmed, which verify the proposed method. It can help designers to gain more intuitions and insights on multi-loop systems from both circuit and device perspectives, which is also an effective tool for both stability analysis and circuit design.