PLL circuit with deadlock detection circuit

摘要

Disclosed is a PLL circuit including a deadlock detection circuit includes a counter circuit for counting a clock signal. In a deadlock state, the deadlock detection circuit outputs a deadlock detection signal responsive to an output signal from the counter circuit when the counter circuit has counted a preset number of the clock signal. The deadlock detection signal serves to release the PLL circuit from the dead lock. During the normal operation, the counter circuit does not impart noise to the PLL circuit.