A CMOS Dual- RC Frequency Reference With ±200-ppm Inaccuracy From -45 °C to 85 °C

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Abstract

This paper presents a 7-MHz CMOS RC frequency reference. It consists of a frequency-locked loop in which the output frequency of a digitally controlled oscillator (DCO) is locked to the combined phase shifts of two independent RC (Wien bridge) filters, each employing resistors with complementary temperature coefficients. The filters are driven by the DCO's output frequency and the resulting phase shifts are digitized by high-resolution phase-to-digital converters. Their outputs are then combined in the digital domain to realize a temperature-independent frequency error signal. This digitally assisted temperature compensation scheme achieves an inaccuracy of ±200 ppm from -45 °C to 85 °C after a two-point trim. The frequency reference draws 430 μA from a 1.8-V supply, while achieving a supply sensitivity of 0.18%/V and a 330-ppb Allan deviation floor in 3 s of measurement time.
Original languageEnglish
Article number8472141
Pages (from-to)1-10
Number of pages10
JournalIEEE Journal of Solid State Circuits
Volume53
Issue number12
DOIs
Publication statusPublished - 2018

Keywords

  • CMOS
  • digital frequency-locked loop (FLL)
  • digitally controlled oscillator (DCO)
  • integrated frequency reference
  • RC-based

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