Spur reduction in bang-bang PLLs using programmable bit-stream
All-digital bang-bang phase-locked loops (PLLs) are prone to spurious output tones. In this reported work, a programmable bit-sequence is generated and used as a time-mode dithering signal. The bit-stream can be programmed to emulate the required order of a ΣΔ modulator operating in the time-domain without need for any hardware change. This method leads to a low-cost, compact, low-power and versatile phase noise-shaping scheme.