一种采用电流缓冲器的反嵌套密勒补偿型LDO

An LDO using reverse nested miller compensation with current buffers

为了提高低压差线性稳压器(low dropout regulator,LDO)在全负载电流范围内的稳定性,提出了一种采用电流缓冲器的反嵌套密勒补偿结构(reverse nested miller compensation with current buffers,RNMCCB)的LDO,外部补偿环使用电流镜作为反相电流缓冲器,内部补偿环使用共栅级放大器作为电流缓冲器。该补偿结构不需要额外的晶体管,保证了LDO的负反馈性质;引入两个左半平面的零点,增加了电路的相位裕度。仿真结果表明,在轻载(1 mA)至重载(600 mA)、输出电容为0.1~5μF环境下,最小相位裕度为38°,输出电压的下冲为10.6 mV,上冲为11.7 mV,达到设计要求。

In order to improve the stability of the low dropout regulator(LDO)over the full load current range,we propose an LDO using reverse nested miller compensation with current buffers(RNMCCB).A current mirror was used as an inverting current buffer in the outer compensation loop,and a common-gate amplifier was used as a current buffer in the inner compensation loop.The proposed structure did not require any additional transistors.The negative feedback nature of the LDO was guaranteed by using this compensation structure.This structure created two left half plane zeros and increased the phase margin.The simulation results show that the minimum phase margin is 38°under light load(1 mA)to heavy load(600 mA)and the on-chip output capacitance from 0.1 to 5μF,the undershoot and overshoot of the output voltage are 10.6 mV and 11.7 mV.