A Fully Integrated Fast-Response LDO Voltage Regulator with Adaptive Transient Current Distribution

A fully integrated low-dropout (LDO) regulator with fast transient response is proposed in this paper. The capacitor-less LDO (CL-LDO) regulator incorporates both assisted pass-transistors and control circuit to realize adaptive transient current distribution during the load current transition, thereby enhancing the transient response and minimizing the output voltage's spike. In 65-nm CMOS process, the CL-LDO regulator occupies an active area of 0.0088 mm2. It supplies an output voltage of 1.2 V, while the input supply ranges from 1.5 V to 2.5 V. Subjected to a 100 μA ± 10 mA step change of load current with 1-μs rise time and fall time, the regulator can settle the output to a stable voltage within 1.1 μs and the output voltage's spike is reduced to less than ± 20 mV. The line regulation and load regulation of this regulator are 0.52 mV/V and 0.01 mV/mA, respectively.