A Subharmonically Injection-Locked All-Digital PLL Without Main Divider

A subharmonically injection-locked all-digital phaselocked loop (ADPLL) without a main divider is presented. It achieves not only low power but also low phase noise over the process, voltage, and temperature (PVT) variations. This ADPLL uses only a simple bang-bang phase detector without a time-todigital converter when both frequency and phase locking. Moreover, the injection pulse can be self-adjusted to optimal timing over the PVT variations without additional calibration loop. This ADPLL is fabricated in a 40-nm CMOS process; it consumes 3.04 mW under a standard supply of 1.1 V excluding output buffers. The measured phase noise of the proposed ADPLL is -121.4 dBc/Hz at 1-MHz offset. The integrated RMS jitter is 109.6 fs for the offset frequency from 1 kHz to 100 MHz. The calculated figure-of-merit is equal to -254.39 dB.