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:
Dec. 19, 2000
Filed:
Jul. 19, 1999
Masaki Sano, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
A phase locked loop has a charge pump circuit connected through a loop filter to a voltage controlled oscillator, and the charge pump circuit is controlled by a frequency/phase comparator, wherein the charge pump circuit includes a first current mirror circuit responsive to a first control signal for regulating a discharging current from the loop filter to a first target amount proportional to a constant current, a second current mirror circuit for regulating a reference current to a second target amount proportional to the constant current and a third current mirror circuit responsive to a second control signal for regulating a charging current to the loop filter to a third target amount proportional to the reference current, a first switching circuit for charging a first parasitic capacitor coupled to the first current mirror circuit from the constant current source and a second switching circuit for charging a second parasitic capacitor coupled to the third current mirror circuit through the second current mirror circuit, thereby setting a limit on a spike current generated at a change of the first and second control signals.