Design And Simulation Of High-precision LDO

With the continuous development of integrated circuit industry,a variety of power management chip has also been greatly developed.Currently,power management chips used in portable electronic products mainly includes DC-DC switching regulator,charge pump type voltage regulator,LDO(low dropout regulator)and PMU(power management unit).Because of its advantages of simple structure,high stability,small ripple,low cost,low noise,small volume,small static current,and can be easily integrated in other chips,LOD has been well developed.The accuracy of foreign LDO products is generally ±2% or ±1%,the accuracy of domestic LDO products is generally ±2%,compared to foreign products,the accuracy of domestic LDO products is relatively low.This paper is based on the CSMC(Central Semiconductor Manufacturing Corporation)0.5?m CMOS process design a LDO product.The precision of the product is ±1%,the input voltage is in the range of 3.3V to 6V,the output voltage is 3V,the working temperature is between-40? to +85?,ripple rejection ratio is 65 dB @10k Hz,the maximum output current is 150 mA,the static current is 50?A,the standby current is less than 0.1?A.The main task is to design a high precision LDO,by consulting the relevant literature,the author found that the method of improving the accuracy of voltage is mainly to improve the precision of reference voltage source and the gain of error amplifier.To improve the accuracy of reference voltage source is mainly to reduce the influence of temperature.In the design,the author adopted a depleted enhanced voltage reference to shield the effects of temperature on the reference voltage source,and designed a high stability voltage reference which is minimally affected by temperature.In order to improve the gain of error amplifier,the design of the error amplifier using cascode Operation Trans conductance two-stage amplifier.In order to improve the stability of LDO under large current,the large size PMOS is adopted as the adjusting tube,which reduces the conduction resistance of the adjusting tube.In order to reduce the standby power consumption,added the enable module in LDO,so that in the standby mode,the other modules are all closed except the enable module,in order to achieve the purpose of reducing the standby current.In addition,the current limiting circuit module is designed,which can protect the LDO when the LDO overload or short circuit occurs.The final design of the LDO consists of enable module,reference voltage source,error amplifier,adjustment tube,bias voltage module,feedback resistance network and current limiting circuit module.Through the simulation of the design,the LDO's input voltage range is in the range of 3.3V to 6V,output voltage is 3V,working temperature is between-40? to +85?,the ripple rejection ratio is 69 dB @10 KHZ,maximum output current is 300 m A,static current is 50?A,idle current is less than 2n A,leakage voltage is within 0.29V@300m A,linear adjustment rate is 0.122%/V,accuracy of LDO is ±0.9%,all the indicators meet the design requirements.Although the design indicators have reached the requirements,but there are still in need of improvement.Due to the main pursuit of design indicators,other design parameters are not carefully considered,such as linear regulation parameters and so on are yet to be improved.