Adaptively Biased Output Cap-Less NMOS LDO with 19 ns Settling Time

Debashis Mandal, Chirag Desai, Bertan Bakkaloglu, Sayfe Kiaei

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

This paper presents an output external capacitor-less, fully integrated, fast settling NMOS low-dropout (LDO) regulator with adaptively biased error amplifier (EA) for system-on-chip core applications. The adaptive biasing technique increases both loop bandwidth and slew-rate of the LDO by 100% at full load condition without changing no-load quiescent current. Direct feedback to gate-to-source voltage of the NMOS regulation FET provides fast load transient response. The proposed LDO employs a cross-coupled common-gate input based EA, with transconductance boosting, achieving twice unity-gain bandwidth in comparison to a typical folded-cascode common-source input stage. Low output impedance of NMOS regulation stage and low input impedance of the EA reduce load dependent stability issue. The proposed regulator is designed and fabricated in a 0.18-μm CMOS technology with die-area of 0.21 mm2. The LDO generates a regulated output voltage of 1.4-1.6 V from an input voltage of 1.6-1.8 V, consumes 133 μA quiescent current, and supports 0 pF to 50 pF load capacitance. Measured results show 166 mV undershoot with 19 ns settling time for a load step from 9 mA to 40 mA in 350 ps edge-time for zero-load capacitance. After using adaptive biasing, the settling time is reduced by 37% and 36% for 0 pF and 50 pF load, respectively.

Original languageEnglish (US)
Article number8370135
Pages (from-to)167-171
Number of pages5
JournalIEEE Transactions on Circuits and Systems II: Express Briefs
Volume66
Issue number2
DOIs
StatePublished - 2019

Keywords

  • Adaptively biased error amplifier
  • NMOS lowdropout (LDO) regulator
  • cross-coupled common-gate input stage
  • fast load transient response
  • fast slew-rate

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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