Projeto de um conversor digital-analógico current-steering segmentado de 8-bits para aplicações biomédicas

Abstract

This work presents the design of a digital-to-analog converter (DAC) capable of sending electrical neurostimulation signals to the neurological system. This device will have the ability to attenuate or reduce the deficiencies that cause the failure of electrical contacts between the axons and, thus, alleviate the difficulties faced by patients who suffer from degenerative diseases of the sensory nervous system, such as Parkinson's disease. The concepts and techniques for implementing and improving the data converter will be multiplied, which will carry out the intercommunication between the control module and the neural pathway. This project uses an 8-bit segmented currentsteering DAC designed in a 180-nm CMOS technology with a maximum stimulation current of 255 uA. The use of a binary-to-thermometer decoder designed with transistor- level logic gates was necessary to control the built with logic gates at a transistor level, was necessary to control the switching of cells and its constructive diagram is presented. The improvements and optimizations of this converter were carried out through the analysis of the output current curve, attenuating the switching noises by advancing the switching between the deviation of the current sources of the cells and the definition of the best sizing of the current sources transistors through Monte Carlo simulations. current source via Monte Carlo simulations. The variability test of static characteristics was performed and it was found that the DAC presented a maximum INL / DNL of 1.5 / 1 LSBs for 500 simulation runs. Separate analysis of those circuits, the circuits specification and design data are also provided in this work.