A dynamically phase adjusting PLL with a variable delay

Phase locked loops (PLLs) are widely used for many purposes. The lock-up performance is one of the most important target items in designing PLLs. In a digital PLL, it is difficult to control the frequency and phase independently, which makes it difficult to improve lock-up performance. A variable delay circuit which adjusts only the phase of the PLL is introduced here. A full loop model simulation with measured controllable delay shows the effectiveness of applying the phase adjust method with the variable delay to the PLL.