A 12.9-to-15.1-GHz Digital PLL Based on a Bang-Bang Phase Detector With Adaptively Optimized Noise Shaping

This work introduces a bang-bang fractional-Nphase-locked loop with quantization noise shaping that overcomes the classical noise limit of a standard bang-bang phase detector. An adaptive algorithm, working in the background of the main system, guarantees optimal noise shaping across process and environmental variations. The prototype, implemented in a standard 28-nm CMOS process, has a core area of 0.21 mm2and achieves an rms jitter (integrated from 1 kHz to 100 MHz) of 69.5 fs for integer-Nsynthesized channels, 79.7 fs for typical fractional-Nchannels, and 99.6 fs for near-integer fractional channels with a worst case fractional spur of −51.1 dBc. The power consumption is 10.8 mW, leading to a jitter-power figure of merit of −252.8 dB and −251.6 dB for integer-Nand fractional-Nchannels, respectively.