A low dropout voltage regulator with a transient voltage spikes reducer and improved figure of merit

Authors: GURU PRASAD, KUMARA SHAMA

Abstract: An area efficient output capacitor-free low dropout [LDO] voltage regulator with an improved figure of merit is presented in this paper. The proposed LDO regulator consists of a novel, dynamically biased error amplifier that reduces overshoot and undershoot voltage spikes arising from abrupt load changes. Source bulk modulation is employed to enhance the current driving capability of the pass transistor. An adaptive biasing scheme is also used along with dynamic biasing to improve the current efficiency of the system. The on-chip capacitor required for proper working of the LDO regulator is only 35 pF. The proposed LDO regulator is designed and simulated in 180 nm standard CMOS technology. The LDO regulator exhibits a line regulation of 1.67 mV$\mathbin{/}$V and a load regulation of 100 $\mu {V}\mathbin{/}$mA. When load changes from 0 mA to 100 mA in 1 $\mu $s, an undershoot of 148 mV and an overshoot of 172 mV are observed. The measured power supply rejection ratio is 25 dB at 100 kHz. The working of the proposed LDO regulator has been tested under all process corners and Monte-Carlo statistical analysis reveals that it is robust against process variations and local mismatch.

Keywords: Dynamic biasing, adaptive biasing, source bulk modulation, output capacitorless, figure of merit, low dropout voltage regulator

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