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An output-capacitorless low-dropout regulator (LDO) with a direct voltage-spike detection circuit is presented in this paper. The proposed voltage-spike detection is based on capacitive coupling. The detection circuit makes use of the rapid transient voltage at the LDO output to increase the bias current momentarily. Hence, the transient response of the LDO is significantly enhanced due to the improvement of the slew rate at the gate of the power transistor. The proposed voltage-spike detection circuit is applied to an output-capacitorless LDO implemented in a standard 0.35-Â¿m CMOS technology (where VTHN Â¿ 0.5 V and VTHP Â¿ -0.65 V). Experimental results show that the LDO consumes 19 Â¿A only. It regulates the output at 0.8 V from a 1-V supply, with dropout voltage of 200 mV at the maximum output current of 66.7 mA. The voltage spike and the recovery time of the LDO with the proposed voltage-spike detection circuit are reduced to about 70 mV and 3 Â¿s, respectively, whereas they are more than 420 mV and 30 Â¿s for the LDO without the proposed detection circuit.
Date of Publication: Feb. 2010