| 摘要 |
PURPOSE:To form various signals required for the NTSC, the PAL and the SECAM systems by switching an oscillating frequency of a reference oscillation circuit and a frequency dividing ratio of a frequency divider depending on each system to use one kind of a semiconductor integrated circuit device. CONSTITUTION:The reference frequency signal formed by the oscillation circuit OSC is applied to a phase comparator circuit PC via frequency division circuit DV1, DV2 and compared with an output of a frequency division circuit DV3. An output of the comparator PC is fed back to a voltage control oscillator VCO via the LPF and its output is fed to a counter CONT via the frequency dividers DV3 and DV4. The oscillation frequency of the oscillation circuit OSC and the frequency dividing ratio of the frequency dividers DV2, DV3 are set to different values depending on the NTSC, the PAL and the SECAM systems. The output frequency of the oscillator VCO is different from the three systems and a signal required for each system is outputted from the counter CONT. Moreover, branching frequencies fCS1-fCS3 are used selectively as chrominance subcarrier signals. |
