基于高摆率误差放大器的低功耗LDO设计

Design of low power LDO based on high swing rate error amplifier

本文设计了一种具有低静态电流的低压差线性稳压器(LDO).针对传统LDO在低静态电流下瞬态响应不足的问题,电路中的误差放大器采用两个共栅差分跨导单元交叉耦合连接进行设计,提高其压摆率;利用体偏置运放改变功率管的阈值电压实现功率管在不同负载的快速切换;同时采用动态偏置对电路进行偏置减少过欠冲值.电路采用台积电(TSMC)0.18µm互补金属氧化物半导体(CMOS)工艺进行设计,版图核心面积为220µm×140µm.仿真结果表明,该LDO在最小负载电流与最大负载电容的组合下相位裕度达到100度,消耗的静态电流仅为849 nA.当负载电流在500 ns时间内从100µA到100 mA进行切换时,电路表现出良好的瞬态响应,其中过冲电压为220 mV,欠冲电压为225 mV.经过计算,品质因数(FOM)值为0.198 mV.

In this paper,a low-voltage differential Low DropOut regulator(LDO)with low static current is designed.In order to solve the problem of inadequate transient response of traditional LDO under low static current,two common-gate differential transconductance cells are cross-coupled as the error amplifier to improve the swing rate and the body-biased operational amplifier is used to change the threshold voltage of the power transistor to achieve fast switching.At the same time,the dynamic bias is used to offset the circuit to reduce overshoot and undershoot.The circuit is designed by TSMC 0.18µm Complementary Metal Oxide Semiconductor(CMOS)technology and the core area of the layout is 220µm×140µm.The simulation results show that the phase margin of the LDO is 100 degrees under the combination of minimum load current and maximum load capacitance,and the static current consumed is only 849 nA.When the load current is switched from 100µA to 100 mA within 500 ns,the circuit shows good transient response,in which the overshoot is 220 mV and the undershoot is 225 mV.After calculation,theFigure Of Merit(FOM)value is only 0.198 mV.