Transient Response Enhancement on the Output-Capacitorless Low-Dropout Regulator Using the Multipath Nested Miller Compensation with a Transient Quiescent Current Booster

Chun-Hsun WU  Le-Ren CHANG-CHIEN  

IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.9   pp.1464-1471
Publication Date: 2011/09/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.1464
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electronic Circuits
CMOS analog ICs,  DC-DC power conversion,  capacitorless low-dropout regulator,  

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Low drop-out regulators (LDOs) are widely used in the system-on-a-chip (SoC) design. Due to the multi-function and energy saving requirements for mobile applications nowadays, more strict specifications are expected on the developmental roadmap of the LDOs. An output-capacitorless LDO providing fast transient response under the low supply voltage and low quiescent current conditions is proposed in this paper. Provided by the low supply voltage, the proposed LDO adopts cascading technique using the Multipath Nested Miller Compensation (MNMC) to maintain a higher bandwidth for fast transient requirement. In addition, a Transient Quiescent Current Booster (TQCB) is supplemented to the operational amplifier to improve the slew rate for the fast load transient. The TQCB only raises the quiescent current during the load transient instant so that both power saving and the load response improvement could be well achieved. It deserves noting that the proposed TQCB contains only two transistors, which is simple to be implemented compared to the other transient current enhancement techniques. The designed LDO has only 1.6 pF capacitance for the totally added on-chip compensation, and 25.8 µA of current consumption in the main amplifier. The recovery time under the fast load change is less than 3 µs and the stability is guaranteed. Test results from the real implementation of a 0.35 µm CMOS process verify that the designed LDO performs as expected.