基于有源反馈补偿的快速瞬态响应LDO设计

Design of a fast transient response LDO based on active feedback compensation

为实现全负载范围的稳定性并增强瞬态响应性能,设计了一款基于有源反馈频率补偿的无片外电容低压差线性稳压器(LDO)。有源反馈将通过补偿电容的信号放大,有效减小了补偿电容的大小。采用自适应偏置电路检测负载变化来提高瞬态响应,同时结合电容耦合方式的瞬态增强电路给功率管栅极提供额外的泄放路径,进一步减小轻载到重载切换时的下冲电压值。电路设计基于SMIC 180 nm BCD工艺,实现了输入电压范围为1.4~2 V,输出电压为1.2 V。仿真结果表明,当负载电容为100 pF时,在0.5μs时间内负载由0到100 mA之间跳变,输出电压的最大过冲值和下冲值分别为102.5 mV和160.5 mV,恢复时间分别为1.6μs和1μs。

To achieve full load range stability and enhance transient response performance,a capacitor-less low dropout regulator(LDO)was proposed based on active feedback frequency compensation.The signal passing through the compensation capacitor was magnified by an active feedback block,which effectively reduced the size of the compensation capacitor.An adaptively biased circuit was used to detect the load changes to improve the transient response.To further reduce the undershoot during light load to heavy load switching,the transient enhancement circuit utilizing capacitive coupling was also adopted to provide an additional discharge path for the gate of the power transistor.The presented LDO design was modeled in SMIC 180 nm BCD process with an input voltage of 1.4-2 V,an output voltage of 1.2 V,and a maximum load current of 100 mA.Simulation results show that when the load capacitance is 100 pF,the maximum overshoot and undershoot are 102.5 mV and 160.5 mV for full load current changes within 0.5μs edge time with recovery time of 1.6μs and 1μs,respectively.