A High Power Supply Rejection and Low Noise Low-Dropout Regulator for Voltage Controlled Oscillator

Low-dropout regulator (LDO) is normally used to provide good supply quality for voltage controlled oscillator (VCO). In this work, the requirements of PSR and output noise of LDO are analyzed and obtained by restricting the deterioration of VCO's phase noise. Then the PSR of the LDO is modeled and a method to get high PSR and low output noise LDO is proposed. Finally, a capacitor-less LDO is designed by using the proposed method with a standard 28 nm CMOS process. The PSRs of designed LDO are - 81 dB at 10 kHz and - 41 dB at 1 MHz, respectively. The integrated noise is 3.9 µVrms among the frequency range of 10 Hz ~ 100 kHz. The LDO has a small output capacitor of 15 pF, and the quiescent current is only 100 μA.