On Chip Monitoring for Efficient Thermal Management

Abstract

Temperature is a critical physical parameter frequently monitored in electronic systems due to its substantial impact on performance and power consumption. In recent years there has been great effort to enhance the technology for development of temperature sensors. Partic- ularly, CMOS-compatible realizations have emerged as a promising alternative, showcasing different physical mechanisms for temperature sensor implementation, including BJTs, Ther- mal diffusivity and MOSFETs. MOSFET-based temperature sensors offer several advantages, such as low-voltage operation, high energy efficiency, and a compact footprint. Although they may sacrifice resolution and accuracy, this trade-off aligns with the prevalent trend in advanced System-On-Chips designed for Internet-of-Things (IoT) nodes, where these parameters can be relaxed since the priority is energy efficiency while being fully-integrated by handling directly a digital readout, also known as smart temperature sensors. This thesis focus on designing and evaluating energy-efficient smart temperature sensors based on MOSFET devices. The research encompasses two main achievements. The first involves a smart temper- ature sensor focused on low-voltage and low-power operation, with a nominal 350 mV of supply voltage and a power consumption of just 14 nW at 25 ◦C with a silicon footprint of 0.049 mm2, a resolution of 0.27 ◦C and achieving a Resolution Figure-of-Merit (R-FoM) of 0.034 nJ·K2. This sensor is tailored to meet the stringent constraints of IoT applications.. The second achievement focuses on a compact sensor targeted for Dynamic Thermal Management. The circuit exhibits a wide supply voltage operating range from 0.6 V to 1.8 V with an energy per conversion of 1.06 nJ, noise-limited resolution of 0.24 ◦C, a silicon area of 0.021 mm2, and an a R-FoM of 0.061 nJ·K2. The latter characteristic is particularly notable given the area constraint and the sensor’s ability to operate across a broad range of supply voltages