A High-Efficiency and Fast-Transient Low-Dropout Regulator With Adaptive Pole Tracking Frequency Compensation Technique

An advanced smooth pole tracking technique for a low dropout (LDO) regulator with a ceramic capacitor is presented in this article. Normally, the dominant pole is at the output of an LDO and becomes load dependent, which may cause a loop stability issue during the whole load-current application range. The proposed frequency compensation methodology with adaptive load resistor control of an error amplifier (EA) alleviates the problem and reduces the dependence of equivalent series resistance of an output capacitor. Moreover, combined with this compensation strategy, an ultrafast EA by utilizing a transconductance enhancement technique is proposed to greatly reduce output voltage spikes as well as response time of the LDO during transient. This circuit has been implemented in a 0.18-mu m standard CMOS process and occupies an active chip area of 0.017 mm(2). Experimental results show that it can deliver 150 mA load current at 200 mV dropout voltage. Good loop stability and transient responses are easily achieved without degrading other important LDO parameters.