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. 21, 1999
Filed:
Mar. 06, 1997
Masaaki Soda, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
Besides a frequency-phase comparator for input and VCO signals, a filter for a frequency-phase difference signal, and a VCO controlled by a filter output signal to produce a phase locked VCO signal, a PLL circuit comprises a VCO controller for controlling an oscillation frequency range of the VCO when the input and the VCO signals are continuously in collapse of synchronism longer than a predetermined time interval, such as a pull-in time of the PLL circuit, with the collapse detected by the comparator. Preferably, the VCO comprises an inverter loop, each inverter delay controlled by the filter output signal and a loop length controlled by a VCO control signal. The VCO controller comprises an up-down counter for counting up or down a count signal decoded into the VCO control signal with the count counted up and down depending on whether the frequency-phase difference signal indicates, when the predetermined time interval is measured by a timer started upon occurrence of a collapse, that the VCO signal is higher or lower in frequency than the input signal.