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Title: A reference-sampling based calibration-free fractional-N PLL with a PI-linked sampling clock generator
Authors: Han, Jae-Soub
Eom, Tae-Hyeok
Choi, Seong-Wook
Seong, Kiho
Yoon, Dong-Hyun
Kim, Tony Tae-Hyoung
Baek, Kwang-Hyun
Shim, Yong
Keywords: Engineering::Electrical and electronic engineering
Issue Date: 2021
Source: Han, J., Eom, T., Choi, S., Seong, K., Yoon, D., Kim, T. T., Baek, K. & Shim, Y. (2021). A reference-sampling based calibration-free fractional-N PLL with a PI-linked sampling clock generator. Sensors, 21(20), 6824-.
Journal: Sensors 
Abstract: Sampling-based PLLs have become a new research trend due to the possibility of removing the frequency divider (FDIV) from the feedback path, where the FDIV increases the contribution of in-band noise by the factor of dividing ratio square (N2). Between two possible sampling methods, sub-sampling and reference-sampling, the latter provides a relatively wide locking range, as the slower input reference signal is sampled with the faster VCO output signal. However, removal of FDIV makes the PLL not feasible to implement fractional-N operation based on varying divider ratios through random sequence generators, such as a Delta-Sigma-Modulator (DSM). To address the above design challenges, we propose a reference-sampling-based calibration-free fractional-N PLL (RSFPLL) with a phase-interpolator-linked sampling clock generator (PSCG). The proposed RSFPLL achieves fractional-N operations through phase-interpolator (PI)-based multi-phase generation instead of a typical frequency divider or digital-to-time converter (DTC). In addition, to alleviate the power burden arising from VCO-rated sampling, a flexible mask window generation method has been used that only passes a few sampling clocks near the point of interest. The prototype PLL system is designed with a 65 nm CMOS process with a chip size of 0.42 mm2. It achieves 322 fs rms jitter, -240.7 dB figure-of-merit (FoM), and -44.06 dBc fractional spurs with 8.17 mW power consumption.
ISSN: 1424-8220
DOI: 10.3390/s21206824
Schools: School of Electrical and Electronic Engineering 
Rights: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:EEE Journal Articles

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