Crystal oscillator for low-voltage applications

TCC(graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Engenharia Eletrônica.Em virtude do recorrente aumento de aplicações para IoT (Internet das Coisas), que exige dispositivos autossuficientes, este trabalho de conclusão de curso propõe o projeto de um circuito integrado de baixa tensão que, combinado a um cristal de quartzo, forma um oscilador, o qual é um bloco importante em sistemas digitais e de comunicação. Esse circuito opera com 100mV de tensão de alimentação, compatível com o uso de dispositivos de colheita de energia, visto que esses dispositivos geram tensões de dezenas a centenas de milivolts. Por operar em baixa tensão, o consumo de potência do circuito diminui. Este trabalho apresenta a teoria, medições práticas usando componentes discretos e o projeto do circuito integrado, em conjunto com simulações de esquemático e layout, que permitem verificar o comportamento do circuito integrado e suas condições de operação.Given the increase of IoT applications, which requires autonomous devices, this final year project proposes the design of a low-voltage integrated circuit that, combined with a quartz-crystal, forms an oscillator, an important block in digital and communication systems. The circuit operates with 100 mV of supply voltage, which is compatible with the use of energy harvesting devices, since these devices provide from tens to hundreds of millivolts. By operating at low-voltages, the circuit’s power consumption is reduced. This work presents the theory, measurements using discrete components and the design of the integrated circuit of a Pierce oscillator along with schematic and layout simulations, which allows to verify and predict the behavior of the integrated circuit

Bridging the Gap between Design and Simulation of Low-Voltage CMOS Circuits

This work proposes a truly compact MOSFET model that contains only four parameters to assist an integrated circuits (IC) designer in a design by hand. The four-parameter model (4PM) is based on the advanced compact MOSFET (ACM) model and was implemented in Verilog-A to simulate different circuits designed with the ACM model in Verilog-compatible simulators. Being able to simulate MOS circuits through the same model used in a hand design benefits designers in understanding how the main MOSFET parameters affect the design. Herein, the classic CMOS inverter, a ring oscillator, a self-biased current source and a common source amplifier were designed and simulated using either the 4PM or the BSIM model. The four-parameter model was simulated in many sorts of circuits with very satisfactory results in the low-voltage cases. As the ultra-low-voltage (ULV) domain is expanding due to applications, such as the internet of things and wearable circuits, so is the use of a simplified ULV MOSFET model

Bridging the gap between design and simulation of MOS circuits: implementation of the ACM model in Cadence and the associated extraction of parameters

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2021.Modelos compactos do MOSFET são essenciais para o projeto e simulação de circuitos integrados. O modelo BSIM é amplamente utilizado em ferramentas EDA para executar simulações de circuitos MOS. Sua complexidade, tanto no que se refere ao grande número de parâmetros quanto a seus significados, no entanto, abre uma lacuna entre a simulação de circuito e o projeto executado pelo projetista, tornando difícil entender como os principais parâmetros do MOSFET se relacionam com os resultados finais. Para facilitar o entendimento do projetista quanto aos principais parâmetros que intervêm no projeto, este trabalho propõe um modelo simplificado do MOSFET, baseado no modelo Advanced Compact MOSFET (ACM), contendo apenas 4 parâmetros. A extração dos 4 parâmetros do modelo é realizada através de simulações automatizadas no simulador Cadence® Virtuoso®. Finalmente, para preencher a lacuna entre projeto e simulação, o modelo de 4 parâmetros foi implementado em Verilog-A para simular diferentes circuitos projetados com base no modelo ACM. Quatro circuitos foram simulados: inversor CMOS, oscilador em anel, fonte de corrente autopolarizada (SBCS) e amplificador de baixo ruído (LNA). Os resultados de simulação são apresentados e comparados com os resultados obtidos com o modelo BSIM. O modelo de 4 parâmetros destina-se, principalmente, à modelagem para ultra-baixa tensão (ULV) porque os efeitos secundários suprimidos não são tão acentuados no domínio ULV, o qual abrange pesquisas sobre aplicações de colheita de energia, redes de sensores para a Internet das Coisas e circuitos always-on.Abstract: Compact MOSFET models are essential for design and simulation of integrated circuits. The BSIM model is widely used in EDA tools to run MOS circuit simulations. However, its complexity, regarding the huge number of parameters and their meanings, opens a gap between circuit simulation and hands-on design, making it hard to understand how the main MOSFET parameters are related to the simulation results. In order to assist the designer in understanding how the main MOSFET parameters affect the design, this work proposes a simplified MOSFET model, based on the Advanced Compact MOSFET (ACM) model, which contains only 4 parameters that are extracted through automated simulation setups on Cadence® Virtuoso® simulator. Finally, to bridge the gap between design and simulation, the 4-parameters model was implemented in Verilog-A to simulate different circuits designed with basis on the ACM model. To test the appropriateness of our proposal, four circuits (a CMOS inverter, a ring oscillator, a self-biased current source (SBCS) and a low-noise amplifier (LNA)) were simulated, either using the 4-parameter ACM model or the BSIM model. The simulation results demonstrate that the 4-parameter model is mostly suitable for ultra-low voltage (ULV) modeling. This is because some of the secondary effects not included in the 4-parameter model are not so accentuated in the ULV domain, which comprises applications such as energy harvesting, sensor nodes for the Internet of Things and always-on circuits

Bridging the Gap between Design and Simulation of Low-Voltage CMOS Circuits

This work proposes a truly compact MOSFET model that contains only four parameters to assist an integrated circuits (IC) designer in a design by hand. The four-parameter model (4PM) is based on the advanced compact MOSFET (ACM) model and was implemented in Verilog-A to simulate different circuits designed with the ACM model in Verilog-compatible simulators. Being able to simulate MOS circuits through the same model used in a hand design benefits designers in understanding how the main MOSFET parameters affect the design. Herein, the classic CMOS inverter, a ring oscillator, a self-biased current source and a common source amplifier were designed and simulated using either the 4PM or the BSIM model. The four-parameter model was simulated in many sorts of circuits with very satisfactory results in the low-voltage cases. As the ultra-low-voltage (ULV) domain is expanding due to applications, such as the internet of things and wearable circuits, so is the use of a simplified ULV MOSFET model