大电流负载的片上LDO系统设计

摘要

This paper analyzes the stability and transient response enhancement limit of traditional LDO system and a tran-sient response enhancement technique of on-chip LDO system is presented .Based on the analysis ,a transient response enhancement technique fully integrated on-chip is put forward .The proposed scheme not only results in stability within a wide range of load varia-tion ,but also gets a good ripple rejection without off-chip capacitor and equivalent series resistor .It is demonstrated by simulation that the proposed circuit dissipates only 64μA of quiescent current with empty load and it is capable of delivering load current up to 800mA ,the power supply rejection rate at 1KHz is about -60dB .For a load step of 800mA/5μs ,the circuit has a maximum under-shoot of 400mV and a maximum overshoot of 536mV .The recovery time is only 6.7μs and 12.8μs respectively and the layout area is about 0.64mm2 .%本文分析了传统大电流负载的LDO （Low-dropout Regulator ）系统实现系统稳定性和瞬态响应提高的局限性，在此基础上，提出了一种片内集成的瞬态响应提高技术．此技术无需外挂电容和等效串联电阻（Equivalent Series Resistor ，ESR），即能使系统在全负载范围内保持稳定性和良好的纹波抑制能力．仿真结果表明，系统空载时，静态电流为64μA ，且最大能提供800mA的负载电流，1KHz时的电源抑制比达到-60dB ，当负载电流以800mA/5μs跳变时，最大下冲电压为400mV ，上冲电压为536mV ，恢复时间分别只需6.7μs和12.8μs ，版图面积约为0.64mm2．