A Noise Reconfigurable All-Digital Phase-Locked Loop Using a Switched Capacitor-Based Frequency-Locked Loop and a Noise Detector

Programmability is one of the most significant advantages of a digital phase-locked loop (PLL) compared with a charge-pump PLL. In this paper, a digital PLL that extends programmability to include noise is introduced. A digitally controlled oscillator (DCO) using a switched capacitor for frequency feedback is proposed to maintain a constant figure of merit while reconfiguring its noise performance. The proposed DCO offers an accurate and linear frequency tuning curve that is insensitive to environmental changes. A noise detection circuit using the statistical property of a bang-bang phase and frequency detector is proposed to autonomously adjust the output noise level depending on the noise specification. A prototype design is fabricated in a 28-nm FDSOI process. The integrated phase noise of the proposed PLL can be configured from 2.5 to 15 ps, while the power consumption ranges from 1.7 to 5 mW.