The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 20, 2004
Filed:
Nov. 18, 2002
David Y. Wang, San Jose, CA (US);
Jyn-Bang Shyu, Cupertino, CA (US);
Neoaxiom Corporation, San Jose, CA (US);
Abstract
A method and a lock detector circuit for phase-locked loop for detecting lock between reference signal and a feedback signal in two phases: lock detection phase and lock assertion phase. The detector circuit comprises delay circuits coupled to a first, a second D flip flops, an OR logic gate, and an AND gate. In the lock detection, the lock detector circuit compares the phases of the reference input clock with the feedback clock. If the phases of these clocks are different or not within a window of tolerance, the sample clock outputs of the first and second D flip flops are different. This condition causes the logic gate to issue a reset signal to the divide-by-64 counters. As such, the lock detection signal is low, indicating the PLL is not in lock condition. In the lock assertion phase, if the two phases are the same or within the window of tolerance, the sample clock outputs of the first and second D flip flops are the same or both low at the same time. This condition causes the logic gate to issue an enabling signal to the divide-by-64 counters. The divide-by-64 counter starts to count to full cycle and then the lock detect signal is high, indicating the PLL is in locked condition.