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:
Sep. 13, 2011
Filed:
Aug. 19, 2009
Pengfei HU, Shanghai, CN;
Song Gao, Shanghai, CN;
Pengfei Hu, Shanghai, CN;
Song Gao, Shanghai, CN;
Integrated Device Technology, Inc., San Jose, CA (US);
Abstract
A clock circuit includes a phase-lock loop and a holdover circuit. The phase-lock loop generates an output clock signal having a constant frequency based on a loop filter voltage of a loop filter in the phase-lock loop. The holdover circuit generates and stores a digital value indicating the loop filter voltage and generates an analog voltage signal having the loop filter voltage indicated by the digital value. Further, the holdover circuit maintains the output clock signal at the constant frequency during a holdover of the phase-lock loop by regenerating the loop filter voltage based on the analog voltage signal. Because the analog voltage signal is based on the digital value, the voltage of the loop filter does not decay over time during the holdover of the phase-lock loop. As a result, the output clock signal remains at the constant frequency during the holdover of the phase-lock loop.