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PLL synthesizing oscillator (3)
Block diagram of the top is a clickable image map.
You can jump to each page of the explanation when you click each block.
I introduce the PLL synthesizer oscillator by MC14046B which can change the frequency.
The PLL oscillator can be made using three kinds pieces of the ICs like the figure above. Because most of the functions are stored in the ICs, there are few, too, circumference circuits and the making is easy.
The BCD(Binary Coded Decimal) switch is used to change the frequency.
Because the phase comparison frequency is 1KHz, the output frequency can be changed with the 1KHz step.
Each IC is equipped with the following function.
|Reference frequency oscillator
It is the crystal oscillator by the inverter circuit.
The reference frequency this time is 4.096 MHz.
|Reference frequency divider
|It divides the reference frequency in 4096(212) and it makes the phase comparison frequency of 1KHz.
It compares the reference frequency by 4060 and the comparison frequency by 4522 by the phase.
When there is a difference, it outputs the revision pulse.
It controls to make low when the oscillation is high-frequency and to make high when low-frequency.
It is the voltage controlled oscillator.
At the control voltage from the phase comparator, the oscillation frequency changes.
It divides the output of the VCO and it creates the phase comparison frequency.
It specifies the dividing ratio by the BCD.
This time, it uses three pieces of 4522 and the dividing ratio of 3-digit (0-999) is made to be able to be specified. The effective range is 10-999.