Invention Grant
US07714625B2 System and method for fast re-locking of a phase locked loop circuit 有权
用于快速重新锁定锁相环电路的系统和方法

System and method for fast re-locking of a phase locked loop circuit
Abstract:
A system and method for reducing the re-lock time of a phase locked loop (PLL) system, the system including a circuit having a capture control voltage module, a force control voltage module, a loop filter module, and a timer. The capture control voltage module compares the control voltage (voltage input of VCO) with predefined voltage levels during the lock time of the PLL and simultaneously stores the voltage level closest to the control voltage. The stored voltage becomes stable after the PLL has been locked. After power-down is applied and then released, the force control voltage module forces the stored control voltage on the loop filter in a very short time, thereby reducing the re-lock time of the PLL. The loop filter module stabilizes the control voltage. The timer then turns off the force control voltage module by sending a timeout signal after a pre-defined number of clock cycles.
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