Design Of Low Power And High PSRR Wireless Energy Management Unit

With the improvement of living standards,people pay more attention to health problems,which makes the study of implantable medical chips more attractive.One of the research hot spots is the collection and management of wireless energy,which avoids the problem of limited battery-powered energy in the traditional sense.By collecting external RF signal energy and rectifying and boosting,a more stable DC level is obtained,thereby providing a working power for the implanted chip.This thesis first describes the significance of wireless energy management unit,introduces the research status of wireless energy management unit at home and abroad,and analyzes the overall architecture and basic principles of wireless energy management unit and the performance index based on implantable medical chip design.Finally,based on0.18μm CMOS process for the overall circuit design.The wireless energy management unit is composed of three sub-circuits: Charge Pump Rectifier(CPR),Bandgap Voltage Reference(BGR)and Low Dropout Regulator(LDO).The contents of the work are as follows:(1)Research and design of charge pump rectifier.The basic principle of traditional CPR and the reason of low energy conversion efficiency are analyzed.An improved CPR with threshold voltage elimination technology is proposed.Post-simulation results show that the six-level CPR conversion efficiency is 25.3%,the minimum input voltage amplitude as low as 0.3V.(2)Research and design of low power,high power supply rejection ratio(PSRR)bandgap reference source.Based on the analysis of the basic principle of traditional voltage mode structure BGR,a hybrid BGR based on sub-threshold MOS transistor and bipolar transistor is proposed.Then,a very low power PSRR auxiliary circuit is proposed to further optimize the BGR performance.The post-simulation results show that the temperature coefficient of the improved reference source is 21.8ppm/℃,the absolute error under different process corners is 1.6%,the input voltage range is 0.75 V ~ 2V,the PSRR is-104 d B@ DC,-90 d B @ 500 MHz,the final power consumption is only 0.85 u A.(3)Research and design of Low-power,high power supply rejection ratio low-dropout regulator.The coupling path of LDO power supply ripple and the optimization effect of ZPTC on LDO bandwidth are analyzed emphatically.Then in turn designed over-temperature protection,current-limit protection and over-voltage protection circuit.Finally,PSRR auxiliary circuit in BGR is used to further optimize PSRR performance ofLDO.The simulation results show that the LDO output voltage is 1.2V at a load current of30 u A,the minimum input and output voltage drop is 0.238 V,the PSRR is-94 d B @ DC,-60 d B @ 500 MHz and the quiescent current is only 3.418 u A.(4)Research and design of wireless energy management unit.Integrate CPR,BGR and LDO into a complete wireless energy management unit for full layout simulation.After the simulation results show that increasing the input AC signal amplitude,CPR output voltage is always limited to between 1.8V ~ 2V.Under typical conditions,CPR output voltage ripple is5.74 m V,LDO output voltage ripple is only 6.13 u V,the maximum load current is 30 u A.Finally,when the temperature exceeds 70℃ or the current exceeds 40 u A,the circuit will be automatically shut down.