An Injection-Locked Ring-Oscillator-Based Fractional-N Digital PLL Supporting BL

Abstract

This article presents an injection-locked (IL) ring- oscillator-based fractional- N digital phase locked loop (DPLL) supporting Bluetooth low energy (BLE) frequency modulation with an frequency-shift keying (FSK) error between 2.4% and 3.3%. As the fractional spur cannot be suppressed by IL-DPLL, this work proposes a random edge injection (REI) to reduce the spur . This technique also speeds up the convergence time of gain calibration of the digital-to-time converter (DTC). Furthermore, the prop