A 1V, 1mW, 4GHz Injection-Locked Oscillator for High-Performance Clocking

Injection-locked clocking (ILC) has been proposed previously to improve the skew and jitter performance while reducing the power consumption in multi-gigahertz clock distribution networks. This paper presents a new design of the injection-locked oscillator (ILO) suitable for ILC applications. It uses a transformer to generate differential signals and then directly inject them into the ILO core. It also incorporates a switched-capacitor array for frequency tuning and hence digital deskew in ILC. A 4 GHz test chip was designed and fabricated in a 0.18 mum standard digital CMOS. It consists of four ILOs driven by a balanced H-tree. Each ILO consumes less than 1 mW from a 1 V power supply. 5-bit digital deskew achieves 55 ps delay tuning range and 1.8 ps resolution. Measurement shows that only 30 fs cycle-to-cycle jitter degradation was introduced and no phase noise degradation at frequency offset up to 600 kHz.