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:
Feb. 19, 2013
Filed:
Aug. 24, 2011
Hiroyuki Nakamoto, Kawasaki, JP;
Hiroyuki Ito, Yokohama, JP;
Hiroyuki Nakamoto, Kawasaki, JP;
Hiroyuki Ito, Yokohama, JP;
Fujitsu Limited, Kawasaki, JP;
Fujitsu Semiconductor Limited, Yokohama, JP;
Abstract
An oscillation circuit has a first inverter connected to an external piezoelectric resonator, a first feedback resistor disposed between input/output terminals of the first inverter, first/second variable capacitive elements connected to input/output of the first inverter, a charging circuit supplying input/output terminal with a reference current to charge the capacitive element, a comparator comparing a charging voltage of input/output with a reference voltage, and a control circuit that, in a calibration operation, at a first time, causes the charging circuit to start supply the reference current to the input terminal or the output terminal, and, at a second time after the first time, generates the control signal for setting a capacitance value of the first or second variable capacitive element so that the charging voltage becomes close to the reference voltage according to a comparison result of the comparator.