Patent Number: 7,042,300

Title: Oscillator circuit, semiconductor device and semiconductor memory device provided with the oscillator circuit, and control method of the oscillator circuit

Abstract: There is provided an oscillator circuit capable of obtaining stable frequency by avoiding output having unstable frequency that is likely to occur to an operation/stop-control-feasible type oscillator circuit when oscillation begins. In such an oscillator circuit, an oscillation permitting signal (EN) sets an oscillator section in oscillation-operable state, whereby a controller section starts operation. The controller section that has stared its operation change an oscillation-frequency control signal (VR) into a signal value corresponding to predetermined oscillation frequency so as to set oscillation frequency at an oscillator section. Further on, the oscillator section outputs an oscillation signal in response to a detection signal (MON) that is outputted after a detector section compares a signal inputted therein with a predetermined signal value and detects that the inputted signal reaches a predetermined signal value. Thereby, transient state of an oscillation-frequency control signal (VR) can be detected. That is, there can be avoided an output of an unstable oscillation signal due to a transient oscillation-frequency control signal (VR).

Inventors: Ogawa; Yasushige (Kasugai, JP), Kawamoto; Satoru (Kasugai, JP)

Assignee: Fujitsu Limited

International Classification: H03B 5/00 (20060101); H03B 5/24 (20060101)

Expiration Date: 5/09/02018