Energy-Efficient Circuits for IoT Systems

Internet of things (IoT) has greatly improved our understanding and control of the world. By deploying sensors to the environment, different types of environmental parameters can be sensed and with proper processing of the data, such as artificial intelligence, we can observe and control at both the top-level and detail. However, various IoT applications also pose lots of challenges for the integrated circuit design, especially for the power efficiency, speed and size. Solving these problems are the keys to turn the ideas into real and practical design and improve the user experience.In this dissertation, the circuits and systems design of the IoT sensor is presented and discussed. The power management unit (PMU) is an important block in an IoT sensing system, which determines the maximum performance of the circuit. For lots of applications where it is hard to replace the battery and has limited energy source, the efficiency of the PMU also significantly affects the system lifetime. A fast-response-time, high-power-efficiency and dynamic-range change-pump-based LDO is proposed to solve the trade-off between speed, power consumption and stability. The event-driven mechanism and AC-coupled high-Z feedback loop enable fast detection and response speed with low power. The charge-pump with single power transistor architecture helps the LDO achieve a high dynamic range and low ripple over the entire load range. In addition to the power management unit, the clock generation circuit also significantly affects the system performance and power efficiency. Several techniques are proposed to achieve an energy-efficient fast start-up. With the multi-path feedforward negative resistance boosting and dynamic pulse-width injection technique, the start-up time of different frequency XOs can be greatly reduced without a precise injection oscillator. Last, a battery-powered ion-sensing platform is presented and discussed