Russlk said:
The CD4046 is not strictly digital because it has an analog filter. You could make an all digital PLL with a microprocessor (PIC) using digital integration or Z transforms. (Don't ask me how to do that!)
I agree. Lots of people refer to the 4046 as a digital PLL. It also has an analog VCO, so it doesn't match mit_mohit's definition.
A synthesizer with a numerically controlled oscillator is another "digital PLL", but I'm pretty sure the VCO output is from a D/A converter, which is analog.
As Russ said, an all-digital PLL is possible, but I have never seen one.