A Switched-Capacitor DC-DC Converter Powering an LC Oscillator to Achieve 85% System Peak Power Efficiency and -65 dBc Spurious Tones

Alessandro Urso, Yue Chen, Robert Bogdan Staszewski, Johan F. Dijkhuis, Stefano Stanzione, Yao-Hong Liu, Wouter A. Serdijn, Masoud Babaie

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Abstract

In this paper, we propose a new scheme to directly power a 4.9-5.6GHz LC oscillator from a recursive switched-capacitor DC-DC converter. A finite-state machine is integrated to automatically adjust the conversion ratio and switching frequency of the converter such that its DC output voltage is within ±5% of the desired 1V across input voltage range 1.3-2.2V and < 2mA load current conditions. A gate-driver circuit is embedded in each switch of the converter to guarantee constant on-resistance across PVT variations without sacrificing device reliability. Furthermore, a spur reduction block (SRB) is embedded in the oscillator to suppress the ripple induced spurs by stabilizing its tail current. Both the converter and the oscillator are implemented in 40-nm CMOS technology. The measured peak power efficiency of the converter is 87%, while its spot noise is < 1.5nV/Hz which does not degrade the phase noise of the oscillator. The SRB suppresses the spur to <-65dBc under the 30mVpp ripple of the converter.

Original languageEnglish
Pages (from-to)3764-3777
Number of pages14
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume67
Issue number11
DOIs
Publication statusPublished - 2020

Keywords

  • LC oscillator
  • LDO replacement
  • Switched-capacitor DC-DC converter
  • gate-driver circuit
  • phase noise
  • spur reduction block
  • voltage controlled oscillator (VCO)

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