Data Conversion With Subgate-Delay Time Resolution Using Cyclic-Coupled Ring Oscillators

Vishnu Unnikrishnan, Okko Jarvinen, Waqas Siddiqui, Kari Stadius, Marko Kosunen, Jussi Ryynanen

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)
112 Downloads (Pure)


An integrated circuit that measures time intervals with high precision and accuracy has a wide range of applications including data conversion, ranging, and 3-D imaging. The resolution with which time intervals are quantized by a ring oscillator or delay line is limited by the minimum delay of an inverter in the technology. We propose the use of cyclic-coupled ring oscillators (CCROs) as a time-domain quantizer to achieve a combination of subgate-delay time resolution together with a short conversion time, thereby enabling data conversion with high resolution as well as high bandwidth. The resolution-power tradeoff in coupled oscillators is studied. Simulation indicates up to a factor-of-13 subgate-delay time resolution with 13 coupled oscillators. A real-time quantizing time-to-digital converter with coupled oscillators is designed for a time-domain analog-to-digital converter. Powered by a factor-of-8 subgate-delay time resolution of 1.6 ps obtained with nine coupled oscillators, and a sample time of 4 ns for 11-bit conversion, the converter delivers a 9.9-bit ENOB over a signal bandwidth of 125 MHz and an SFDR of 88 dB. Results demonstrate that CCROs is an attractive candidate as a high-precision high-linearity time-domain quantizer for data converters.

Original languageEnglish
Article number9269488
Pages (from-to)203-214
Number of pages12
JournalIEEE Transactions on Very Large Scale Integration (VLSI) Systems
Issue number1
Publication statusPublished - Jan 2021
MoE publication typeA1 Journal article-refereed


  • Analog-to-digital converter (ADC)
  • cyclic coupled ring oscillator (CCRO)
  • data converter
  • oscillator
  • oscillator-based
  • ring oscillator
  • subgate-delay
  • technology-independent
  • time resolution
  • time-domain
  • time-of-flight (ToF)
  • time-to-digital converter (TDC)
  • ToF sensor
  • VCO-based ADC.


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