A Fast Low Dropout Regulator with High Slew Rate and Large Unity-Gain Bandwidth

Abstract

A low dropout regulator (LDO) with fast transient responses is presented. The proposed LDO eliminates the trade-off between slew rate and unity gain bandwidth, which are the key parameters for fast transient responses. In the proposed buffer, by changing the slew current path, the slew rate and unity gain bandwidth can be controlled independently. Implemented in 0.18-mu m high voltage CMOS, the proposed LDO shows up to 200 mA load current with 0.2 V dropout voltage for 1 mu F output capacitance. The measured maximum transient output voltage variation, minimum quiescent current at no load condition, and maximum unity gain frequency are 24 mV, 7.5 mu A, and higher than 1 MHz, respectively.