Research And Design Of Low Drop-out Linear Regulators

With the growing popularity of electronic products, power ICs become more and more important.The Low dropout linear regulator is widely used in commuication equipment,auto electronic parts,medical equipment and test equipment.It have some advantages such as low drop-out voltage,high precision,low noise,high integration,high performance price ratio and simple structure.It has a broad market prospect.A reference voltage uses pump,improving accuracy.The quiscent current is only 1.42 ? A.By designing and selecting of regulator,PMOS is used of rugulator.So it makes dropout voltage lower,only 76 mA. error amplifier uses two differential amplifier circuit,improving gain.The gain is 38 dB.Dynamic zero frequency compensation methods are studied to ensure the stability of the whole system.The phase margin is 80°.In order to protect the security of chip,over-current protection circuit and anti-static circuit are designed.By using a soft-start circuit and Schmitt trigger,the input voltage can be adjusted.In the paper,the whole circuit is simulated by using Candence software.The output voltage is 1.8V.The input voltage range is 1.8V to 5.5V.The maximum output current is 200 mA and quiescent current is 1.42?A,The dropout voltage is 76 mV.The line regulation is 1.1%,while load regulation is 11%,PARR is-46 dB.Simulate result show that the design result matchs design request.The test of the chip proves that this regulator can provide a steady output voltage, both the overcurrent protection function and anti-static function can come ture.