A Class-AB LDO regulator with high stability suitable for multiple input reference voltages

A Class-AB LDO capable of sinking/sourcing current from/to the load is presented. Unlike conventional LDO structures, the input reference voltage of this circuit is adjustable and has a wide adjustment range. The circuit has been demonstrated in a 0.35 um BCD process at a 3.3 V supply voltage. Its low-frequency sourcing 10 mA current, sinking 10 mA current and no-load PSRR are -80.3 dB, -106.1 dB, and -83.4 dB, respectively. The voltage undershoot is 69 mV when the output changes from sinking 10 mA to sourcing 10 mA in 10 us, and the overshoot is 64 mV for the opposite process. The minimum phase margin is 50 degrees at 0.1-10 mA load current. The area of the entire LDO circuit is 0.28 mm 2 , including the protection circuit.