Lock detector for phase locked loops

In a phase locked loop of the type including a phase detector configured to develop phase error signals for use by at least a loop filter in deriving control signals for an oscillator circuit, a method for evaluating phase detector output so as to optimally determine when phase lock has been achieved the method comprising:

• acquiring the absolute magnitude of each phase error signal comprising the output signal train of a phase detector;
• comparing the absolute magnitude of each phase error signal with a specified phase error maximum value;
• initiating a time interval count at any time the absolute magnitude of a phase error signal falls below the error limit value;
• declaring a lock condition when the time count exceeds a specified time interval;
• wherein the time count returns to a zero time value at any time the absolute magnitude of any phase error signal exceeds the maximum error limit value;
• wherein the comparison step further comprises:
• arithmetically summing the absolute magnitude of each phase error signal with a negative valued first limit signal;
• and
• comparing the summation to a reference signal.