Analysis, modeling, and design of RF-DC micro-power power management unit for RFID and micro-sensor applications

RFID and micro-sensor networks need high-efficiency and low-cost integrated circuits to improve system performance and reduce the cost for massive deployment. The RF-DC power management unit (PMU), although a critical building block of the RFID tag or sensor system, however, has not been studied in sufficient details before. In this research, a systematic study of PMU design is presented, covering all basic building blocks. First, area-efficient topologies of PMUs that meet accuracy requirements are identified for reducing cost. Two new topologies, namely, the split-storage-capacitor and dual-power-path topologies are proposed, both of which could reduce the sizes of storage capacitors by 20-50%. Second, design methodology for the optimal design of UHF micro-power CMOS rectifiers is derived, without resorting to extensive and time-consuming simulations. A multiple-output rectifier using a 0.18μm process is designed, fabricated and tested to verify the analysis. Third, area-efficient bandgap voltage references (BGRs) with ultra-low power (100nW) are studied using a systematic classification. Existing BGRs are categorized and new BGRs are easily generated. Features such as the availability of multiple reference voltages, temperature-independent reference current and proportional to absolute temperature (PTAT) current are also considered. Noise computation shows that some BGRs have better noise performance under the same current consumption, and are better candidates for RFID and micro-sensor applications. An untrimmed BGR is fabricated and measured. Fourth, other building blocks such as low-dropout regulators, DC-DC charge pumps, protection circuit, power-on-reset circuit, and power detector are investigated and designed. Design considerations are discussed, and appropriate topologies and circuits are proposed and/or identified. Fifth, two PMUs using the developed topologies and building blocks are designed and fabricated in a 0.18μm process. Measurement results verify the proper functioning of the PMUs in the context of RFID tag system. To conclude, this research addresses the important issues of analysis, modeling, and design of RF-DC micro-power power management units for RFID and micro-sensor applications