A Design And Research Of High Performance And Integrated PMU For The Silicon-based Micro-display Chip

With the rapidlly development of microelectronic technology in recent years,OLED-on-silicon micro-display equipment has attracted people's attention with the advantages of its micro portability.Because the OLED-on-silicon pixel driving circuit needs positive and negative voltage supply to achieve the display effect,the positive voltage required for pixel driving circuit and the negative voltage needed for OLED-on-silicon common cathode.The purpose of this project is to design a dual output power management unit(PMU).Firstly,introduces the type of converter,the commonly used PMU include: low dropout linear regulator(LDO),charge pump and DC-DC switching,analyzes this three kinds of converter performance,and combined with the actual requirement of the project,the new structure of PMU combination Cuk DC-DC converter and LDO,The Cuk circuit adopts PWM modulation and peak current control mode to output negative voltage,At the same times,the pulse voltage produced by the Cuk circuit is filtered to get the DC voltage,the DC voltage through the LDO module to output positive voltage,both two output voltage is higher in value than the input voltage.The PMU circuit consists of two parts: the first part is LDO module that output positive voltage,include bandgap reference circuit,error amplifier and resistor feedback network submodules in LDO,by analyzing the factors that affect the stability of LDO circuit,a LDO structure with Miller compensation is designed;The second part use PWM modulation to output negative voltage,The submodules of this part include the current detection circuit,slope compensation circuit,error amplifier,comparison amplifier,ring oscillator and the driving circuit,etc.Because the negative output part adopts the double loop negative feedback structure which is outer ring voltage and inner loop current,so we use voltage loop compensation network and current loop slope compensation circuit to ensure that the negative part of PWM modulation has enough phase margin.The PMU is designed under SMIC 0.18?m 1.8V/5V CMOS mix-signal process.With the 3.3V input power voltage,the output voltage has an adjustable positive voltage range of 2~5.5V along and a negative voltage range of-2~-5.5V.The simulation results show that the output ripple of voltage is less than 5m V.The positive and negative voltage output linear regulation is 5m V/V and 20 m V/V.Also,a load regulation of 0.04 m V/m A and 0.15 m V/m A is designed to meet the PMU specification.