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.

I. Introduction

With the development of communication electronic products, the demands for high-quality power supply is increasing. The power supply system should own the characteristics of low power consumption and high efficiency to save energy and prolong the battery life, which makes the inductive converter very popular. However, the switching power supply brings high system noise, which cannot be accepted by VCOs, phase locked loops (PLL), and other devices. For example, in PLL, the index of VCO’s phase noise determines the performance of the wireless transceiver. Therefore, the LDO is usually adopted to provide a “clean” power supply to the VCO.