Design Of LDO For Wireless Charging Analog Core Unit

In recent years,the popularity of wireless charging technology has required many requirements of rapid development for all kinds of portable electronic devices.The wireless charging chip’s coupling coil cannot directly supply power to each functional module inside the chip because of its wide input range.A linear dropout regulators circuit is needed which can convert the input voltage into a suitable low voltage and provide bias voltage to internal circuit.And make the internal module of wireless charging chip work normally.Based on the above problems,the main research objective of the thesis is to design a wide input LDO which can be integrated in wireless charging chip.Based on Hua Hong 180 nm BCD process library,the thesis designs a LDO circuit that can be used for wireless charging chip.The LDO has maximum input voltage up to 36 V and also has the advantages of low quiescent current and high output precision.The main work is as follows:1.The thesis designs a pre-regulated circuit to reduce the use of high voltage devices.It adopts band gap reference structure of four pipe coupling circuits to ensure stable output of reference voltage and current of LDO circuit under high voltage input condition.2.The thesis compares three commons bandgap reference structures and deeply studied the Brokaw bandgap reference structure,and then designed a bandgap reference circuit without operational amplifier.This bandgap designed by the principle of compensation can realize the compensation of temperature characteristic curve in high temperature section.It improvs the temperature characteristics of bandgap reference greatly and achieved high precision and low quiescent current index of bandgap reference.3.In order to improve the accuracy and temperature characteristics of the output voltage,the thesis adds modifying resistance which make the LDO circuit has the function of programmable adjustment.It can be adjusted on the temperature characteristic and output voltage according to the actual output deviation.4.The thesis proposes the method of combining bandgap reference with temperature compensation,undervoltage locking,overtemperature protection and other protection circuit structure to realize the characteristics of low quiescent current.It reduces the use of bias current but also provide protection for the normal operation of the LDO circuit.5.The thesis presents a new design scheme of enabling module to ensure the function of LDO circuit.It outputs one enable signal to control LDO circuit by combining the output of undervoltage locking circuit and overtemperature protection circuit with logic operation.This design reduces the difficulty of enabling and protecting multiple outputs in LDO circuit.The thesis designs a LDO circuit and completes the layout drawing and post simulation.The LDO can normally stabilize the voltage to 2.5V with the input voltage range from 5V to 36 V.Its load current range is from 0m A to 300 m A and the static current is 41.5μA.The operating temperature of LDO is from-45℃ to 125℃.Its temperature drift coefficient can reach 4.3ppm/℃ and the layout area is 751μm×489μm.The simulation results meet the requirements of technical indicators.The chip can be tested and packaged when the chip streamed.