A Low Quiescent Current Fast Transient LDO Regulator With Segmented Pass Transistors

This brief proposes a low quiescent current fast transient low-dropout regulator (LDO). The pass field-effect transistor (FET) in the LDO is segmented into three sections to cope with different loads. Under no-load mode, the smallest-sized pass transistor is directly driven by the error amplifier (EA) for low quiescent current. At light- and heavy- load modes, the medium and largest sized pass FETs are respectively switched on by different strength buffers for fast transient response. The proposed LDO is implemented in a $0.18~\mu $ m BCD process with an active area of 0.0875 mm2. The LDO consumes a quiescent current of 25 nA at no-load condition, with an input voltage range of 1.5 V-5.5 V and an output voltage range of 1.2 V-5 V. The measured transient output voltage is 28 mV when load current is switched from 0 mA to 200 mA in 100 ns with $1~\mu $ F load capacitance. The recovery time is about $1~\mu $ s. Compared to reported counterparts, the proposed LDO shows an excellent figure-of-merit (FOM).