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. 13, 2004
Filed:
Nov. 06, 2001
Ravi Kumar, Bangalore, IN;
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A lock detection circuit is disclosed that is capable of detecting when a phase locked loop circuit is in a locked or unlocked condition. The invention comprises an exclusive OR gate, a deglitch unit, a gate circuit, a count lock circuit, a count unlock circuit, and a flip flop circuit. The deglitch unit outputs a clear “clr” signal only when UP signals and DN signals from a phase frequency detector in the phase locked loop circuit are mismatched in time by more than a predetermined period of time. Detection of a locked condition or an unlocked condition is made by processing “clr” signals in the count lock circuit and in the count unlock circuit.