| With the growing popularity of portable electronic products, the demands forpower management ICs is more and more strong. As one of the power managementICs, the Low Dropout Linear Regulator is widely used in portable electronic products,such as, Bluetooth devices, wireless communication tools, audio equipment, PDA(personal digital assistant) and automotive electronics etc. The LDO has low drop-outvoltage, small output ripple, low output noise, low quiescent current, and low costadvantages. Currently, the LDO is moving towards smaller size, lower powerconsumption, higher efficiency and other direction. Therefore, in-depth study ofhigh-performance LDO still has a very important practical significance for itsapplication prospects.Firstly, the research value of the power management ICs is introduced. Then theframework of LDO system is studied, and the performance parameters of each block inthe system is introduced, and the sub-block of the system is designed. Then thestability of LDO linear regulator and several frequency compensation method isstudied. The LDO in this paper is consists of five main sections, including voltagereference, error amplifier, power management, the feedback network and the protectioncircuit. A reference voltage with lower temperature coefficient is designed byintroducing of higher-order compensation. The error amplifier with Millercompensation is designed, which improves the accuracy of the whole system. Theworks of the pass element and selected of the transistor is studied. Several frequencycompensation method is studied to ensure the stability of the whole system. Finally,over-current protection circuit and over-voltage protection circuit are designed.In this paper, the whole circuit is simulated by using Cadence’s Spectre simulationsoftware. The LDO linear regulator operates at3~5V supply voltage and the typicaloutput voltage is3V. The low dropout voltage of the LOD is only50mV. The linearadjustment rate and load regulation rate are0.044%and0.177%, respectively. Thepower ripple rejection ratio of the LDO is-64dB. In addition, this design also meet thedesign requirements for its good transient characteristics and AC characteristics. The simulation results, with CSMC0.5μm CMOS model, indicate that the design has goodperformance. |
