Design of Low-Voltage Low-Dropout Regulator with Wide-Band High-PSR Characteristic

Utilizing a novel unit-gain compensation cell (UGCC) to perform frequency compensation and power supply rejection (PSR) enhancement, a low-voltage high-PSR low-dropout regulator (LDO) is presented in this paper. The proposed UGCC, consisting of a 1 pF on-chip capacitor and six transistors, effectively overcomes the drawbacks that exist in the conventional compensation schemes by generating an internal low-frequency zero. A LDO that adopts this new structure is implemented and simulated using a standard 0.18-mum CMOS process. Simulation results show that the circuit can work properly when the supply voltage is as low as 1.2 V. The PSR over the frequency range of dc to 1 GHz is better than -40dB in all cases at 1.2 V supply voltage. The dropout voltage is 200 mV when the load current is 100mA. Therefore, it is well suited for low-voltage ripple-sensitive applications