A Low-Jitter Injection-Locked Clock Multiplier Using 97-µW Transformer-Based VCO with 18-kHz Flicker Noise Corner

Zheng SUN
Hanli LIU
Dingxin XU
Hongye HUANG
Bangan LIU
Zheng LI
Kenichi OKADA

IEICE TRANSACTIONS on Electronics   Vol.E104-C    No.7    pp.289-299
Publication Date: 2021/07/01
Publicized: 2021/01/08
Online ISSN: 1745-1353
DOI: 10.1587/transele.2020CDP0005
Type of Manuscript: Special Section PAPER (Special Section on Solid-State Circuit Design — Architecture, Circuit, Device and Design Methodology)
injection lock,  frequency multiplier,  IoT,  ultra-low power,  VCO,  transformer,  FoM,  flicker noise,  CMOS,  

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This paper presents a high jitter performance injection-locked clock multiplier (ILCM) using an ultra-low power (ULP) voltage-controlled oscillator (VCO) for IoT application in 65-nm CMOS. The proposed transformer-based VCO achieves low flicker noise corner and sub-100µW power consumption. Double cross-coupled NMOS transistors sharing the same current provide high transconductance. The network using high-Q factor transformer (TF) provides a large tank impedance to minimize the current requirement. Thanks to the low current bias with a small conduction angle in the ULP VCO design, the proposed TF-based VCO's flicker noise can be suppressed, and a good PN can be achieved in flicker region (1/f3) with sub-100µW power consumption. Thus, a high figure-of-merit (FoM) can be obtained at both 100kHz and 1MHz without additional inductor. The proposed VCO achieves phase noise of -94.5/-115.3dBc/Hz at 100kHz/1MHz frequency offset with a 97µW power consumption, which corresponds to a -193/-194dBc/Hz VCO FoM at 2.62GHz oscillation frequency. The measurement results show that the 1/f3 corner is below 60kHz over the tuning range from 2.57GHz to 3.40GHz. Thanks to the proposed low power VCO, the total ILCM achieves 78 fs RMS jitter while using a high reference clock. A 960 fs RMS jitter can be achieved with a 40MHz common reference and 107µW corresponding power.