High accuracy and low power temperature sensor design in deep sub-micron CMOS processes
Date of Issue2016-03-24
School of Electrical and Electronic Engineering
Along with the development of VLSIs, System-on-Chip (SOC) have become larger and smarter. Circuits that are more sophisticated can be realized on a single chip with higher integrability. In order to realize smart control of the systems, on-chip temperature sensors are integrated into the SOCs to provide accurate temperature information. These on-chip temperature sensors are preferred to the external ones for lower cost and easier integration. This thesis proposes four on-chip temperature sensor designs mainly for two different applications. The first proposed design is for the Battery Fuel Gauge application.As the working environment of the applied Battery Fuel Gauge is worse than the other applications, the temperature range can be wide as from -55C to 175C. The first design in this thesis focused on the realization of high accuracy temperature sensor within the large temperature range in the 40nm CMOS process. The deep sub-micron CMOS processes are chosen because the digital circuits will benefit from the process scaling. However, for analog circuit design, many serious issues appear along with the new processes. Some new circuit techniques are employed in the proposed design to overcome the obstacles of the advanced process. According to the measurement results, the proposed temperature sensor achieves inaccuracy of +-0.5C in the applied temperature range. The detailed analysis will be described in Chapter 3. The other application of this thesis is for the WSNs (Wireless Sensor Networks). WSNs are spatially distributed sensors to monitor physical or environment conditions, such as temperature, sound and pressure. The data sensed by the miniaturised sensors is wirelessly transmitted to a remote data terminal for post-processing. As the energy sources of WSNs are usually batteries or embedded energy harvesting blocks, the available energy budget for the temperature sensors is limited. Therefore, the proposed designs will be focusing on the low power power consumption and simplicity that are different from the requirements in the Battery Fuel Gauges. Based on the different requirements, three time-mode temperature sensor designs will be presented in this thesis. The first design is a closed loop switched capacitor time-mode temperature sensor realized in 180nm digital CMOS. Many circuit techniques are utilized to remove the nonlinearity effects. The inaccuracy in the applied temperature range from -55C to 125C is -0.6/0.5C with two point calibration according to the measurement results. In order to further simplify the structures, two other temperature sensor designs are proposed in 65nm CMOS process. The first design in Chapter 5 is an on-chip oscillator based temperature sensor. The second design in Chapter 6 is a duty-cycle-mode temperature sensor. Both designs are focusing on low power and simplicity. From the simulation results, the FOM values are much better than the state-of-the-art ones benefitting from the low current consumption and simplified architectures. Finally, the proposed four designs will be concluded and future work will be discussed.
DRNTU::Engineering::Electrical and electronic engineering::Integrated circuits