Oscillator circuit, semiconductor device and semiconductor memory device provided with the oscillator circuit, and control method of the oscillator circuit
View Patent ↗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).
1. An oscillator circuit comprising:
a delay section for outputting a delay signal, corresponding to an oscillation permitting command with an oscillation permitting signal, to which a predetermined delay time is added;
an oscillator section for starting oscillation operation in response to the delay signal and stopping the oscillation operation in response to an oscillation disabling command with the oscillation permitting signal; and
a controller section for outputting an oscillation-frequency control signal that controls oscillation frequencies of the oscillator section in accordance with the oscillation permitting signal.
2. An oscillator circuit according to claim 1 , wherein the predetermined delay time is same as or longer than time for a signal value of the oscillation-frequency control signal to reach a signal value corresponding to predetermined frequency in accordance with the oscillation permitting signal.
3. An oscillator circuit according to claim 1 , wherein circuit structure of the delay section is equivalent to circuit structure that generates the oscillation-frequency control signal.