Most hobbyist skip over the section on understanding Phase Locked Loops. The problem with PLL’s is that they are generic. There are many things you can do with PLL’s, so many that it’s hard deconvolute what a basic PLL does.
The 4046 has been around for decades. The 74HC4046 is a modernized (but by no means modern) version that can be used at higher frequencies. The built-in oscillator works up to 12mhz.
The 4046 has two basic sections: a voltage controlled oscillator (VCO) and a phase comparator. The VCO takes a voltage input (zero to Vdd) at pin 9 and outputs a signal on pin 4. This oscillator (VCO) can be used without using the rest of the chip.
I configured a test circuit with C1 = 20pf and R1 = 10K ohms.
Here are the frequencies generated at different pin 9 voltages.
1V 1.0424 mhz
2V 2.883 mhz
3V 4.348 mhz
4V 5.403 mhz
5V 5.551 mhz
C1 = 68pf
1V 0.358 mhz
2V 1.214 mhz
3V 1.902 mhz
4V 2.442 mhz
5V 2.512 mhz