A 4.8-GHz Dividerless Subharmonically Injection-Locked All-Digital PLL With a FOM of $-$ 252.5 dB

A subharmonically injection-locked all-digital phase-locked loop (ADPLL) is presented to achieve both low power and low phase noise simultaneously. This ADPLL uses a bang-bang phase detector to maintain the phase locking without a time-to-digital converter, and the dividers can be disabled to reduce the power. In addition, a subharmonically injection-locked technique is used to achieve a low phase noise. This ADPLL is fabricated in a 40-nm complementary metal-oxide-semiconductor technology. Its power consumption is 3.661 mW for a supply voltage of 1.1 V. The measured phase noise is equal to -122.33 dBc/Hz at an offset frequency of 1 MHz. The integrated root-mean-square jitter is 123.4 fs for the offset frequency from 1 kHz to 100 MHz. The calculated figure of merit is equal to -252.5 dB.