University of Oulu

P. Keränen and J. Kostamovaara, "256 × TDC Array With Cyclic Interpolators Based on Calibration-Free 2 Time Amplifier," in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 66, no. 2, pp. 524-533, Feb. 2019. doi: 10.1109/TCSI.2018.2868242

256 x TDC array with cyclic interpolators based on calibration-free 2x time amplifier

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Author: Keränen, Pekka1; Kostamovaara, Juha1
Organizations: 1Circuits and Systems Group, Faculty of Information Technology and Electrical Engineering, University of Oulu, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.9 MB)
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Language: English
Published: Institute of Electrical and Electronics Engineers, 2018
Publish Date: 2018-12-13


This paper presents the design of a CMOS time-to-digital converter (TDC) used in a direct time-of-flight laser radar line receiver consisting of an array of single-photon avalanche diodes (SPADs) and 256 TDCs. The TDCs use the Nutt interpolation method, where the start/stop fine interpolators are based on a cyclic converter architecture. The cyclic converters use a delay-line-based time interval amplifier to double the quantization residue after each quantization cycle. The time amplifier, and the entire TDC array, does not need any biasing nor does the TDC results need any post-processing to provide sub-100-ps precision and uniformity across the TDC array, therefore making the design very robust and appealing for large designs where hundreds of TDCs are needed on a single chip. Fabricated in a 0.35 μm CMOS technology, a single TDC channel occupies an area of 0.03 mm² and consumes a power of 1.17 mW @ 100 kHz measurement rate. The TDC has a measurement range of 640 ns, and with a resolution of 15 bits, the LSB is 20 ps. Linearity is ensured by the Nutt interpolation method while the rms single-shot precision of the TDC channel is 72 ps. Thus, when LIDAR applications are considered, the TDC is capable of providing a range of 96 m with a precision of 1 cm without any post-processing or calibration.

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Series: IEEE transactions on circuits and systems. I, Regular papers
ISSN: 1549-8328
ISSN-E: 1558-0806
ISSN-L: 1549-8328
Volume: 66
Issue: 2
Pages: 524 - 533
DOI: 10.1109/TCSI.2018.2868242
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: This work was supported in part by the Academy of Finland, Centre of Excellence in Laser Scanning Research under Contract 307362 and in part by Business Finland under Contract 2773/31/2015.
Copyright information: This work is licensed under a Creative Commons Attribution 3.0 License. For more information, see