An improved system and method for determining the lock condition of a
Phase Locked Loop (PLL) is described. The lock detect circuit generates a
fast lock detect signal that may be used to detect a transient loss of
lock. The lock detect circuit may also include a phase alignment detect
circuit to detect a misalignment in the phase of a reference clock and a
feedback clock. Additionally, the lock detect circuit may include a
reference clock detect circuit to detect if the reference clock signal is
detected. Output signals from all of the above circuits may be
communicated to a logic circuit in order to create an enhanced lock
detect signal. An extended lock detect signal may also be communicated to
the logic circuit.