A transient-enhanced low-dropout regulator with dynamic current boost technique voltage buffer

In this paper, a dynamic current boost technique voltage buffer is presented to enhance the large signal response of low dropout regulators (LDOs). The proposed buffer consists of AC coupling networks and active RC network. Without consuming excess power, this LDO achieves substantial improvement in load transient response. Meanwhile, an enhanced recycling-folded-cascode (RFC) amplifier is employed due to its higher gain, bandwidth and slew rate. In order to ensure the stability of full load, this design adopts simple Miller compensation with a nulling resistor without external equivalent series resistance. Moreover, this paper makes a detailed analysis of LDO in theory and the extensive experimental data verified it. The proposed LDO is successfully fabricated in SMIC 0.18μm CMOS process. The input voltage is 1.8-2.2V and the maximum load current is 200 mA. The experiment results indicate that the undershoot is 84 mV and there is no overshoot when the load current is varied from 0 to 200 mA within 100 ns under the load of 1μF load capacitor.