A Frequency-Locked Loop Based on an Oxide Electrothermal Filter in Standard CMOS

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The thermal diffusivity of silicon DSi has been used to realize fully-CMOS frequency references. However, due to the temperature dependence of DSi, the accuracy of such frequency references is limited to about 1000 ppm (−55 °C to 125 °C, one-point trim) due to the inaccuracy of the on-chip temperature compensation circuitry. As an alternative, we propose a frequency reference based on the thermal diffusivity of silicon dioxide DOx. Since the temperature dependence of DOx is much less than that of DSi, the resulting frequency reference will be much more stable over temperature. To investigate this idea, a thermal-diffusivity-based frequency-locked loop (FLL) was realized in 0.18-μm CMOS. With ideal temperature compensation, the proposed frequency reference achieves an inaccuracy of 90 ppm (−45 °C to 85 °C, two-point trim). Even with 0.1 °C inaccuracy, which can be achieved by BJT-based temperature sensors, 200 ppm can still be achieved. This demonstrates the feasibility of high-accuracy oxide-based frequency references in standard CMOS.
Original languageEnglish
Title of host publication43rd IEEE European Solid-State Circuits Conference (ESSCIRC 2017)
Place of PublicationPiscataway, NJ
Number of pages4
ISBN (Electronic)978-1-5090-5025-3
Publication statusPublished - 2017
EventESSDERC-ESSCIRC 2017: 47th European Solid-State Device Research Conference - 43rd European Solid-State Circuits Conference - Leuven, Belgium
Duration: 11 Sep 201714 Sep 2017


ConferenceESSDERC-ESSCIRC 2017
Internet address


  • frequency reference
  • oxide
  • thermal diffusivity
  • CMOS

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