| 摘要 |
PURPOSE:To realize a PLL circuit for down converter which can be digitally made into an IC by converting a signal outputted from a phase comparing circuit to a PWM signal by a PWM circuit consisting of a counter and a comparing circuit and supplying this signal to an integrating circuit. CONSTITUTION:A phase comparing circuit 2 digitally compares the phase of data which is outputted from an A/D converting circuit 1 and has, for example, eight bits as a unit and that of an 8-bit frequency divided signal outputted from a frequency dividing circuit 6 with each other. The digital error signal outputted from the phase comparing circuit 2 is inputted to a comparing circuit 11 and compared with the output of a counter 13. The comparing circuit 11 outputs a signal corresponding to the high level when the output of the phase comparing circuit 2 is larger than that of the counter 13, and the circuit 11 outputs a signal corresponding to the low level when the output of the circuit 2 is smaller than that of the counter 13. That is, the comparing circuit 11 outputs the PWM signal corresponding to the error signal. |
