Patent ID: 6943634

Claim:
An oscillation detection circuit for detecting an oscillation mode of an oscillation circuit, comprising: a first current source for producing a first current; a second current source for producing a second current; a capacitor that is connected with a connection point between the first and second current sources, wherein the capacitor is charged in response to the first current and is discharged in response to the second current; a switch arranged between the first current source and the second current, wherein the switch operates to connect the first and second current sources in series or to disconnect them in response to an output signal of the oscillation circuit, so that a signal emerging at the connection point is gradually increased or decreased as the output signal of the oscillation circuit is periodically changed in level in the oscillation mode; and a Schmitt trigger for producing a detection signal based on the signal at the connection point between the first and second current sources, wherein presence of the oscillation mode and a length of time since commencement of the oscillation mode are detected based on the detection signal.