A 0.0055mm2 480µW Fully Synthesizable PLL Using Stochastic TDC in 28nm FDSOI

Dongsheng YANG  Tomohiro UENO  Wei DENG  Yuki TERASHIMA  Kengo NAKATA  Aravind Tharayil NARAYANAN  Rui WU  Kenichi OKADA  Akira MATSUZAWA  

IEICE TRANSACTIONS on Electronics   Vol.E99-C    No.6    pp.632-640
Publication Date: 2016/06/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E99.C.632
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuits and Related SoC Integration Technologies)
AD-PLL,  synthesizable,  stochastic TDC,  standard cell,  automatic place-and-route,  

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A fully synthesizable all-digital phase-locked loop (AD-PLL) with a stochastic time-to-digital converter (STDC) is proposed in this paper. The whole AD-PLL circuit design is based on only standard cells from digital library, thus the layout of this AD-PLL can be automatically synthesized by a commercial place-and-route (P&R) tool with a foundry-provided standard-cell library. No manual layout and process modification is required in the whole AD-PLL design. In order to solve the delay mismatch issue in the delay-line-based time-to-digital converter (TDC), an STDC employing only standard D flip-flop (DFF) is presented to mitigate the sensitivity to layout mismatch resulted from automatic P&R. For the stochastic TDC, the key idea is to utilize the layout uncertainty due to automatic P&R which follows Gaussian distribution according to statistics theory. Moreover, the fully synthesized STDC can achieve a finer resolution compared to the conventional TDC. Implemented in a 28nm fully depleted silicon on insulator (FDSOI) technology, the fully synthesized PLL consumes only 480µW under 1.0V power supply while operating at 0.9GHz. It achieves a figure of merit (FoM) of -231.1dB with 4.0ps RMS jitter while occupying 0.0055mm2 chip area only.