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:
May. 26, 1998
Filed:
Aug. 19, 1996
Frank David Ferraiolo, Essex Junction, VT (US);
John Edwin Gersbach, Burlington, VT (US);
Charles Joseph Masenas, Essex Junction, VT (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
According to the preferred embodiment of the present invention, a phase-locked loop is provided that overcomes the limitations of the prior art by facilitating fast locking on transition to a different output frequency. The phase-locked loop comprises an oscillator that provides a phase-locked loop output signal at various selected frequencies; a feedback divider; a phase comparator; a memory storage mechanism for storing phase-locked loop control information corresponding to selected output frequencies; and a digital circuit mechanism that receives the control information from the memory storage mechanism on transition to a different output frequency. The control information includes a digital counter value corresponding to the last recorded phase difference of the output signal at the different output frequency. On transition, this information is loaded directly to the digital circuit mechanism, reducing the need and time required for the phase comparator operation to drive the PLL to lock. Thus, the phase-locked loop can quickly achieve phase lock at the different operating frequency.