A 32-MHz, 34-μW Temperature-Compensated RC Oscillator Using Pulse Density Modulated Resistors

Amr Khashaba, Junheng Zhu, Nilanjan Pal, Mostafa Gamal Ahmed, Pavan Kumar Hanumolu

Research output: Contribution to journalArticlepeer-review


Highly stable on-chip frequency references offer the possibility of replacing crystal oscillators in many costand form-factor-constrained applications. However, achieving good frequency stability in a power-efficient manner across process, voltage, and temperature variations possess many design challenges. This article describes these challenges and presents a method for improving the integrated RC oscillator's frequency accuracy by overcoming them. We show that the impact of resistor temperature coefficient (TC) on the accuracy of output frequency can be mitigated by using a parallel combination of two switched resistors that are digitally controlled by pulse-density modulated sequences. By trimming at only two temperatures, a prototype frequency-locked loop (FLL)-based 32-MHz oscillator fabricated in a 65-nm CMOS process achieves an inaccuracy of 530 ppm (8.4 ppm/°C), 80-ppm/V voltage sensitivity, 2.5-ppm Allan deviation, and 1-μW/MHz power efficiency.

Original languageEnglish (US)
Pages (from-to)1470-1479
Number of pages10
JournalIEEE Journal of Solid-State Circuits
Issue number5
StatePublished - May 1 2022
Externally publishedYes


  • Delta-sigma modulator
  • RC oscillator
  • pulse density modulation
  • ring VCO
  • switched capacitor
  • switched resistor
  • temperature compensation

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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