一种基于CLASS-AB类运放的无片外电容LDO设计

Design of a capacitor-less LDO based on CLASS-AB operational amplifier

介绍了一种基于CLASS-AB类运放无片外电容的低压差线性稳压器(LDO)。电路在高摆率误差放大器(EA)的基础上,通过构建动态偏置电路反馈到EA内部动态偏置管,大幅改善了LDO的瞬态响应能力,且动态偏置电路引入的左半平面零点保证了LDO的环路稳定性。同时,EA采用过冲检测电路减小了输出过冲,缩短了环路稳定时间。电路基于65 nm CMOS工艺设计和仿真。仿真结果表明,在负载电流10μA~50 mA、输出电容0~50 pF条件下,LDO输出稳定无振荡。在LDO输入2.5 V、输出1.2 V、无片外电容条件下,控制负载在10μA和50 mA间跳变,LDO输出恢复时间为0.7μs和0.8μs,下冲和上冲电压为58 mV和15 mV。

This paper introduces a CLASS-AB OPAMP-based Low Drop Regulator(LDO)with no off-chip capacitor.Based on the high swing rate Error Amplifier(EA),a dynamic bias circuit has been constructed to feedback voltage to the internal dynamic bias transistors of EA,which greatly improves the LDO’s transient response capability.Moreover,the left half plane zero-pole introduced by the dynamic bias circuit ensures the LDO’s loop stability.At the same time,the EA adopts overshoot detection circuit to reduce the output overshoot and shorten the loop stability time.The circuit is designed and simulated based on 65 nm CMOS process.The simulation result shows that the LDO output is stable with no oscillation under the condition of 10μA~50 mA load-current and 0~50 pF output capacitor.Under the condition of 2.5 V voltage input,1.2 V voltage output,and no offchip capacitor,if the load jumps between 10μA and 50mA,the recovery time of LDO output is 0.7μs and 0.8μs,and the undershoot and overshoot voltages are 58 mV and 15 mV.