A Fast Startup CMOS Crystal Oscillator Using Two-Step Injection

Karim M. Megawer, Nilanjan Pal, Ahmed Elkholy, Mostafa Gamal Ahmed, Amr Khashaba, Danielle Griffith, Pavan Kumar Hanumolu

Research output: Contribution to journalArticlepeer-review


Fast startup crystal oscillators (XOs) are needed in heavily duty-cycled communication systems for implementing aggressive dynamic power management schemes. This article presents the ways to improve startup time of XOs. Using a two-step injection technique in a three-step process, the proposed technique reduces the XO startup time to within 1.5 × the theoretical minimum. By solving the differential equation governing crystal resonator under injection for arbitrary injection frequency, the behavior of energy build-up inside a crystal resonator is analyzed and used to determine optimum injection time as a function of the desired XO steady-state amplitude and injection frequency error. Bounds on tolerable injection frequency error to guarantee the existence of optimal timing are provided. Fabricated in a 65-nm CMOS process, the proposed 54-MHz fast startup XO occupies an active area of 0.075 mm2 and achieves a startup time of less than 20 μs across a temperature range of -40 °C to 85 °C while consuming a startup energy of 34.9 nJ and operating from a 1.0-V supply.

Original languageEnglish (US)
Article number8827914
Pages (from-to)3257-3268
Number of pages12
JournalIEEE Journal of Solid-State Circuits
Issue number12
StatePublished - Dec 2019


  • Crystal oscillator (XO)
  • digitally controlled oscillator (DCO)
  • injection
  • ring oscillator (RO)
  • startup time

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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