Critical analysis to digital approach for bipolar and field-effect based bandgap reference

This work is centered on voltage references, with a particular emphasis on evaluating a digital approach to the bandgap voltage reference. This work was conducted at STMicroelectronics, a renowned leader in semiconductor design and manufacturing. The primary objective of the thesis was to gain a comprehensive understanding of the structure and operation of the digital bandgap voltage reference while also determining its compatibility with lower supply voltages than those typically employed by traditional bandgap cores. To validate these concepts, a series of mixed-signal simulations were performed using the industry-standard tool Cadence Spectre AMS. In order to approach this request effectively, the topology was first simulated at a high level to quantify the impact of each parameter on the overall performance. This involved assessing various design variables and their relationships, after which the component sizing was meticulously carried out. The topology made use of Bipolar Junction Transistors (BJTs) as the physical standard, serving as the reference from which all other voltages were derived in full analogy to the operation of traditional analog bandgap references, ensuring a familiar foundation while exploring digital methodologies. Following an initial phase of thorough investigation into the digital bandgap voltage reference, the focus shifted toward implementing Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) biased in weak inversion or sub-threshold operation. This approach aimed to achieve sub-1V voltage references specifically tailored for low-voltage applications, which are increasingly critical in modern electronic systems. The research subsequently transitioned into designing a robust digital controller tasked with overseeing all operations and states of the structure. Three design approaches were conducted in order to achieve a well-balanced compromise between speed, area, and leakage power. The final part of the thesis was dedicated to coordinating the overall structure along with all its components to ensure the desired functionality. This involved not only integrating the different elements but also validating their interactions to guarantee a seamless operation of the digital bandgap voltage reference.