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. 29, 2003
Filed:
Mar. 03, 2000
Hitachi, Ltd., Tokyo, JP;
Abstract
In order to solve the problem that since a loop filter constant suitable for asynchronous state cannot be selected in the conventional phase frequency synchronism circuit, it takes a long time to synchronize the input data and the clock signal from the asynchronous state, the present invention is to propose a phase frequency synchronism circuit including a phase comparator for generating a voltage according to the phase difference of the clock signal to the input signal, a frequency comparator for deciding if the frequency of the clock signal is higher or lower than the transmission rate of the input signal and generating a binary signal, a synchronous identifying unit for deciding if the input signal and the clock signal are synchronized in their phases and frequencies, a first switch that receives the output from the phase comparator and is closed and opened when the synchronous identifying unit decides that they are synchronized and not synchronized, respectively, a second switch that receives the output from the frequency comparator and is opened and closed when the synchronous identifying unit decides that they are synchronized and not synchronized, respectively, a loop filter that receives the outputs from the first and second switches, and a voltage controlled oscillator that oscillates on the basis of the output from the loop filter.