LARGE-SCALE INTEGRATED CIRCUIT FOR PLL TUNING

摘要

PURPOSE:To prevent the oscillation stop phenomenon of a voltage-controlled oscillator by measuring the output pulse width of a phase comparator and then generating a switching signal, and controlling the application state of a signal to an output circuit on the besis of the switching signal. CONSTITUTION:A PLL circuit consisting of a phase comparator 6 making a phase comparison between the output of a channel selection counter 5 and that of a reference counter 9, and an outputting circuit 1 generating an output signal to an LPF2 on the basis of the comparison result is integrated in a single semiconductor substrate. Then, a control part 12 generates a switching signal on the basis of pulse width information for measuring the pulse width of an out-of- phase pulse from the comparator 6. A control circuit 13 inputs the output pulse from the circuit 6, and the switching signal to generate a control output to the circuit 1.