公开(公告)号：US20150084676A1

公开(公告)日：2015-03-26

申请号：US14034917

申请日：2013-09-24

Applicant: Analog Devices Technology

Inventor： David J. McLaurin ,  Christopher W. Angell ,  Michael F. Keaveney

IPC: H03L7/085 ,  H03L7/10

CPC classification number: H03L7/1976 ,  H03L7/085 ,  H03L7/104 ,  H03L7/199 ,  H03L7/23

Abstract: Apparatus and methods for synchronizing phase-locked loops (PLLs) are provided. In certain implementations, a fractional-N synthesizer includes a PLL and a control circuit that controls a division value of the PLL. The control circuit includes an interpolator, a reset phase adjustment calculator, and a synchronization circuit. The interpolator can control a fractional portion of the PLL's division value. The reset phase adjustment calculator can include a counter for counting a number of cycles of the reference clock signal since initialization of the fractional-N synthesizer, and the reset phase adjustment calculator can generate a phase adjustment signal based on the count. The synchronization circuit can synchronize the PLL in response to a synchronization signal, and can correct for a synchronization phase error indicated by the phase adjustment signal.