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Fast-Transient Digital LDO Regulator With Binary-Weighted Current Control

이진 가중치 전류 제어 기법을 이용한 고속 응답 디지털 LDO 레귤레이터

  • Woo, Ki-Chan (Department of Semiconductor Engineering, Chungbuk National University) ;
  • Sim, Jae-Hyeon (Silliconworks) ;
  • Kim, Tae-Woo (Department of Semiconductor Engineering, Chungbuk National University) ;
  • Hwang, Seon-Kwang (Department of Semiconductor Engineering, Chungbuk National University) ;
  • Yang, Byung-Do (Department of Electronics Engineering, Chungbuk National University)
  • Received : 2016.04.26
  • Accepted : 2016.05.08
  • Published : 2016.06.30

Abstract

This paper proposes a fast-transient digital LDO(Low dropout) regulator with binary-weighted current control technique. Conventional digital LDO takes a long time to stabilize the output voltage, because it controls the amount of current step by step, thus ringing problem is generated. Binary-weighted current control technique rapidly stabilizes output voltage by removing the ringing problem. When output voltage reliably reaches the target voltage, It added the FRZ mode(Freeze) to stop the operation of digital LDO. The proposed fast response digital LDO is used with a slow response DC-DC converter in the system which rapidly changes output voltage. The proposed digital controller circuit area was reduced by 56% compared to conventional bidirectional shift register, and the ripple voltage was reduced by 87%. A chip was implemented with a $0.18{\mu}F$ CMOS process. The settling time is $3.1{\mu}F$ and the voltage ripple is 6.2mV when $1{\mu}F$ output capacitor is used.

본 논문에서는 이진 가중치 전류 기법을 이용한 고속 디지털 LDO(Low Dropout) 레귤레이터를 제안했다. 기존의 디지털 LDO는 일정량의 전류를 한 단계씩 제어하기 때문에 응답하는데 오랜 시간이 걸리며, 링잉 문제가 발생하게 된다. 이중 가중치 전류 기법은 링잉 문제를 제거함으로써 출력전압이 빠르게 안정화되도록 한다. 출력전압이 목표 전압에 안정적으로 도달하면, 디지털 LDO의 동작을 멈추는 프리즈 모드를 추가했다. 제안된 고속 응답 디지털 LDO는 출력 전원 전압이 급격히 바뀌는 시스템에서 응답속도가 느린 DC-DC 변환기와 함께 사용되어 출력전압을 빠르게 변하도록 한다. 제안된 디지털 LDO는 기존의 양방향 시프트 레지스터보다 면적이 56% 감소했고, 리플전압이 87% 감소했다. 제안된 디지털 컨트롤러는 $0.18{\mu}F$ CMOS 공정으로 제작되었다. $1{\mu}F$의 출력 캐패시터에서 정착시간이 $3.1{\mu}F$이고, 리플전압은 6.2mV 였다.

Keywords

References

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