Design Of Core Circuit In ASIC Of Ultrasonic Nebulizer

With the rapid development of social economy,people begin to pay more and more attention to health problems.Atomizing humidifier and atomizing treatment are effective methods to prevent and treat respiratory diseases respectively.Humidifiers moisturize the skin and protect the respiratory tract.Atomization therapy has the advantages of quick curative effect,less dosage and direct action on the diseased parts of the respiratory tract.At present,the driving circuit of ultrasonic nebulizer is mostly comprised of microcontrollers and peripheral circuit.The peripheral driving circuit is complicated,the cost is high,and the reliability is poor.This not only affects the unstable state of the nebulizer when working,but also affects the market competitiveness of the products.Therefore,with the study of the present driving scheme of ultrasonic nebulizer,a new driving scheme is proposed.In the new scheme,the microcontrollers and other peripheral circuits are integrated into one chip to achieve high integration,reduce the area of PCB,and reduce the manufacturing cost.It has the functions of atomization,water level detection,LED lighting effects control,circuit protection,alarm and so on.The ASIC of ultrasonic atomizer designed in this paper is based on CSMC 0.25μm65V BCD process and encapsulated by SOP16,which is verified by SPECTRE.The chip consists of many modules,including Bandgap reference,LDO,oscillator,logic control,nebulization driving,water level detection,LED control,fan control,frequency tracking and protection circuit(UVLO,OCP and OTP).The speed of nebulization and fans are controlled by the variable resistor.In this paper,a novel high voltage bandgap reference is proposed.The standard deviation of the reference voltage offset is 5.7m V,and the variation of the reference voltage is less than 1μV when the supply voltage varies from 4V to 65 V.At the same time,in order to track the resonant frequency of the atomizing piece,the scheme of frequency tracking designed in this paper can achieve the accuracy of 1.7MHz ± 5k Hz.With external resistor and external capacitor,the frequency of the oscillator is accuracy,which makes the frequency tracing easier.In order to ensure that the initial frequency and cut-off frequency is not out of range,the PVT and Monte Carol simulation are necessary.At the same time,the top circuit of the chip is simulated and analyzed.In addition,the theoretical knowledge of layout are summarized in the last chapter,including the procedure of layout design and some points should be paid attention to during layout design,including device matching,reliability and layout rules.According to the theory,the layout of the nebulizer ASIC is designed,and the overall layout is given at last.