Projeto de um regulador de tensão em tecnologia CMOS de 180 nm para circuitos biomédicos implantáveis que empregam transferência de energia sem fio (WPT)

Abstract

This work presents the design of a low-dropout voltage regulator in 180 nm CMOS technology for application in implanted biomedical circuits with wireless energy transfer at an operating frequency of 13.56 MHz. The analyzed voltage regulator is composed of a pass element, a bandgap type voltage reference, an error amplifier and a feedback network. The operating principle and the design procedures of those individual circuits taking into account its impact on the voltage regulator performance are given. The design of two bandgap voltage references and two transconductance operational amplifiers (OTAs) was performed, one being a single stage and the other a two stage with Miller compensation. Thus, it was possible to design four voltage regulators. The designed circuits were simulated at the schematic level with the Spectre simulator to evaluate the voltage regulator performance. The configuration using an OTA-Miller as an error amplifier and a bandgap voltage reference circuit with an operational amplifier has an output voltage of 1.5 V presenting a dropout voltage of 300 mV for a load current of 500 𝜇𝐴. The designed voltage regulator drains 65.44 𝜇𝐴 and exhibits a power supply rejection ratio (PSSR) of 73.96 dB at low frequencies and 14.78 dB at 13.56 MHz. Also, corner and Monte Carlo simulations with 1000 runs were performed to evaluate the voltage regulator behaviour under process variations. The designed voltage regulator was compared with related works designed in 180 nm CMOS technology and achieve similar performance when considering dropout voltage and PSRR.