Ldo (low drop out) having phase margin compensation means and phase margin compensation method using the ldo

A phase margin compensation method using an LDO having a phase margin compensation means including a power supply unit, a reference voltage generation unit, a supply voltage output unit, a comparator, and a duty cycle calculator, the phase margin compensation method comprising:

• a) outputting voltage Vout2 to be applied to a target circuit by receiving and dropping reference voltage Vref as power from the power supply unit by the reference voltage generation unit;
• b) outputting voltage Vout1 actually supplied to the target circuit by receiving and dropping the reference voltage Vref as power from the power supply unit by the supply voltage output unit;
• c) comparing the reference voltage Vout2 output from the reference voltage generation unit with the supply voltage Vout1 output from the supply voltage output unit by the comparator to check whether the supply voltage Vout1 is oscillated and output a pulse signal according to the oscillation of the supply voltage Vout1;
• d) receiving an output signal (pulse signal) from the comparator to count any section of the output signal (pulse signal) by a predetermined frequency by the duty cycle calculator, thereby obtaining the duty cycle ratios and output bits according to the counting and feedbacking the information to the supply voltage output unit;
• e) controlling a phase margin of a frequency of output voltage supplied to the target circuit by feedback-receiving the duty cycle ratios and the output bit information from the duty cycle calculator by the supply voltage output unit and controlling the buffer current based thereon.