| With the rapid development of communication,internet,all kinds of electronic products emerge in endlessly.Electronic products are developing toward miniaturization,low power consumption and the power management chip plays a significant role.Low dropout linear regulators have low power consumption,low noise and fast transient response.Due to their simple structure low dropout linear regulators are widely used in automotive electronics,portable products,mobile phones,wearable electronics,etc.In radio frequency integrated circuits and signal processing circuit,low dropout linear regulators are also often used to provide a clean and stable power supply.This paper designed a low dropout linear regulators.It is mainly composed of current a bias circuit,a bandgap voltage reference circuit,an error amplifier,a power device,resistance of feedback network,etc.These modules constituted a negative feedback loop which was under the action of negative feedback output stable voltage of 2.8 V.This circuit was used in traditional ESR compensation for frequency compensation.In order to maintain the stability of the system and at the same time reduce the ESR resistance,zero pole tracking frequency compensation circuit was added to the circuit.In order to ensure the safety of the circuit,over current,over voltage and over temperature protection circuit was added in.Protection circuit can produce control signal to drive the switch tube.It Ensured low dropout linear regulators working within the normal range.The over voltage and over temperature protection circuit have a hysteresis effect.To produce stable current in the current bias circuit,a differential amplifier was added.The differential amplifier made reference current less sensitive to the change of supply voltage.The bandgap reference current was generated by a negative temperature coefficient current combined with positive temperature coefficient of current.Current was converted into bandgap reference voltage on the resistance.Negative feedback circuit was added in order to improve its power supply rejection ratio in the bandgap reference circuit.The low dropout linear regulators use TSMC 0.18 um CMOS process in this design.Its power working range is 2.92 V to 5.74 V.The dropout voltage is 240 m V when t he output current is 500 m A.The linear adjustment rate is 0.048077%,and the load adjustment rate is 0.31944%.The power supply rejection ratio is 65.22 d B at low frequency.When the temperature is higher than 155 degrees over temperature protection circuit start.When the temperature drops below 135 degrees,the chip returns to work.When the power supply voltage is greater than 5.743 V over-voltage protection circuit starts to work.When the power supply voltage drops below 5.509 V,the circuit is back to normal. |
