Design Of Wide-Input And High-stability LDO

With the development of integrated circuits in China,more and more companies are shifting their targets from consumer electronics to automotive electronics.The automotive electronics application environment is quite different from consumer electronics.The significant difference is that the power supply voltage in automotive electronics is higher than consumer electronics.To make automotive electronics applications safe and stable,the performance of power management chips is particularly important.Linear regulators are widely used because of their simple structure,few peripheral devices,fast response speed,small output ripple,and low cost.In this paper,by studying the basic principle of the voltage regulator and combining the application environment of automotive electronics,a wide-input high-stability LDO for automotive environment is designed.The main work done in this paper is as follows:1.Combined with a wide input voltage application environment,the basic structure of the linear regulator is built.There is a pre-regulation module inside to generate a low voltage for use by other modules;the structure of the power tube adopts the structure of isolation PMOS and high-voltage PMOS in series to withstand high voltage;a buffer stage is added between the output of the error amplifier and the power tube,and the buffer stage converts the lowvoltage loop signal output by the error amplifier into two high-voltage signals for power tube control.2.Integrated over-current protection and over-temperature protection circuits.The overcurrent protection circuit uses an amplifier for loop control to limit the maximum value of the output current to prevent the chip output current from being too high;in an overtemperature state,the output of the over-temperature protection circuit reverses and controls the power tube to be turned off,the chip restarts operation until the temperature is low enough.3.For high stability performance,considering the characteristics of pole distribution in the loop and the demand for large output current,a dynamic zero compensation circuit is added to the main loop of the error amplifier to ensure that the output stability is high enough in the full load range;the overcurrent protection loop also adds a compensation circuit,and the compensation circuit is not directly added to the main loop signal to prevent affecting the normal operation of the main loop.4.In order to improve the efficiency of the linear regulator and reduce the power consumption of the chip,this paper has performed low current processing on all the designed circuits.Without affecting the performance and the function,the current of each module have been reduced as much as possible,so that the final overall current is low enough.5.The performance parameters are verified by simulation and the circuit is adjusted according to the design requirements.The layout of the completed circuit diagram is designed.After the chip is completed,the relevant parameters of the sample are tested and compared with the design requirements.The wide-input high-stability LDO circuit designed in this paper is based on 0.18μm 60 V BCD process,using Cadence for circuit design and simulation.Through simulation verification,the phase margin of the loop reaches more than 40 ° in all change cases of corner,temperature and load current,meet the performance requirements of high stability;use Cadence to complete the layout design,with a total area of 2260μm × 1100μm;finally,the layout was taped out and the chip samples were tested.The test results show that the linear voltage regulator designed in this paper can reach a maximum voltage of 40 V,exhibiting wide input characteristics,a maximum output current of 300 m A,and a static current of 19μA at light load.