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  • A Flexible, Low-Power Analo...
    Shen, Kuan-Yueh; Syed Farooq, Syed Feruz; Fan, Yongping; Nguyen, Khoa Minh; Wang, Qi; Neidengard, Mark L.; Kurd, Nasser; Elshazly, Amr

    IEEE transactions on circuits and systems. I, Regular papers, 07/2018, Volume: 65, Issue: 7
    Journal Article

    This paper presents a PLL supporting diverse low-power clocking needs including wide input (6-200 MHz) and output (0.15-5 GHz) frequency ranges and SSC operation. Fabricated in 14nm FinFET CMOS, a low-power switched-cap loop filter is employed to enable high −3dB PLL bandwidth (>40% of <inline-formula> <tex-math notation="LaTeX">f_{\mathrm{ REF}}=19.2 </tex-math></inline-formula> MHz), and the proposed reference current generator (IrefGen) provides accurate current with <4% tolerance without the need for external components or on-chip precision resistors. IrefGen decouples PLL loop dynamics from feedback divide ratio and provides immunity to systematic capacitor variation. Power gating of switched-cap loop filter's bias circuits results in more than 10% PLL total power savings. The PLL achieves 1.6-ps integrated RMS jitter at 4 GHz using 100-MHz reference while consuming 2.6 mW from 0.95 V. The PLL performance satisfies the stringent PCIe Gen2/3 jitter specifications without resorting to inductors.