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:
Feb. 09, 1999
Filed:
Jun. 23, 1997
Applicant:
Inventors:
Mir Bahram Ghaderi, Cupertino, CA (US);
Vincent W Tso, Milpitas, CA (US);
Assignee:
Exar Corporation, Fremont, CA (US);
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H03L / ;
U.S. Cl.
CPC ...
331 17 ; 331 / ; 331-8 ; 331 25 ; 331D / ; 327156 ;
Abstract
A method and circuitry for detecting when a PLL achieves phase and frequency-lock to a reference frequency with minimal hardware and power dissipation are disclosed. The invention takes advantage of existing blocks within a PLL to reduce the amount of circuitry required while at the same time reducing error due to mismatch. In one embodiment, the present invention combines a coarse lock-detect circuit with a fine lock-detect circuit to achieve fast response when the input reference is lost, while filtering occasional minor phase hits due to external or internal noise.