Design And Simulation Of Cmos-Based Low Voltage Variation Bandgap Reference Voltage Circuitry Using 0.18μm Process Technology

Nowadays, electronics that are able to operate reliably in harsh environments,especially in high temperature environments are in great demand. Electronic systems functioning at extreme temperature requires cooling or heating mechanism from external source. Those thermal management approaches will induce more circuitries into the system and increase the complexity of the overall system. Thus, it is necessary to eliminate the external thermal management circuit and at the same time, ensure that the sensors can operate at wide range of temperature. In this project, Bandgap Reference (BGR) circuit,which are found in on-chip circuitry, is used to produce a constant voltage regardless of temperature, process and supply voltage change. A wide temperature range, which is - 50oC to 140oC, and low voltage variation (1.85mV) of BGR circuit was designed and simulated using Cadence software. The BGR circuit was designed using CMOS compatible process in 0.18μm process technology. A two-stage Operational Amplifier (Op-amp) circuit was designed and incorporated into the complete BGR circuit. The operational amplifier and BGR circuits were simulated using DC and AC analysis in Cadence software. From the graphs plotted, it is found that the BGR circuit proposed is able to operate well at temperature from -50oC to 140oC with only 1.85mV of voltage variation. The proposed circuit has 38.9dB of PSRR and 7.9ppm/oC of Temperature Coefficient. Simulation results are also compared with some state-of-the-art BGR circuits

Low-Power Energy Efficient Circuit Techniques for Small IoT Systems

Although the improvement in circuit speed has been limited in recent years, there has been increased focus on the internet of things (IoT) as technology scaling has decreased circuit size, power usage and cost. This trend has led to the development of many small sensor systems with affordable costs and diverse functions, offering people convenient connection with and control over their surroundings. This dissertation discusses the major challenges and their solutions in realizing small IoT systems, focusing on non-digital blocks, such as power converters and analog sensing blocks, which have difficulty in following the traditional scaling trends of digital circuits. To accommodate the limited energy storage and harvesting capacity of small IoT systems, this dissertation presents an energy harvester and voltage regulators with low quiescent power and good efficiency in ultra-low power ranges. Switched-capacitor-based converters with wide-range energy-efficient voltage-controlled oscillators assisted by power-efficient self-oscillating voltage doublers and new cascaded converter topologies for more conversion ratio configurability achieve efficient power conversion down to several nanowatts. To further improve the power efficiency of these systems, analog circuits essential to most wireless IoT systems are also discussed and improved. A capacitance-to-digital sensor interface and a clocked comparator design are improved by their digital-like implementation and operation in phase and frequency domain. Thanks to the removal of large passive elements and complex analog blocks, both designs achieve excellent area reduction while maintaining state-of-art energy efficiencies. Finally, a technique for removing dynamic voltage and temperature variations is presented as smaller circuits in advanced technologies are more vulnerable to these variations. A 2-D simultaneous feedback control using an on-chip oven control locks the supply voltage and temperature of a small on-chip domain and protects circuits in this locked domain from external voltage and temperature changes, demonstrating 0.0066 V/V and 0.013 °C/°C sensitivities to external changes. Simple digital implementation of the sensors and most parts of the control loops allows robust operation within wide voltage and temperature ranges.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138743/1/wanyeong_1.pd