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:
Nov. 10, 1997
Kozaburo Kurita, Ome, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A PLL circuit includes a phase comparator which makes a comparison between an internal clock signal and a clock signal supplied from an external terminal, a charge pump circuit which produces a charging-up or discharging current in accordance with the output of the phase comparator, so as to drive a filter capacitor, a voltage-controlled oscillator the oscillation frequency of which is controlled by the held voltage of the filter capacitor, and a frequency divider circuit which generates the internal clock signal on the basis of the oscillation output of the voltage-controlled oscillator. The PLL circuit is additionally provided with a voltage detector circuit which detects whether the held voltage of the filter capacitor has been raised to a predetermined voltage or higher, and the function of forcibly lowering the held voltage of the filter capacitor down to a predetermined potential in accordance with the detection output of the voltage detector circuit. Besides, a system is provided with a detection and setting circuit which detects a state brought about by the electrical disconnection of the feedback loop of the PLL circuit, and which brings the PLL circuit into a predetermined state.