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mit_mohit said:Is it posible to design a 'DIGITAL' circuit which functions like a PLL. (i mean no analog components are there.)
If yes then how?
ALso can we design the above said digital circuit without using locally generated clock?
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.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!)
Ron H said: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.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!)
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.
mit_mohit said:OK if a stictly digitalPLL is not available but can we think of some digital circuit which does the job of a PLL
The VCO and the loop filter are the two analog circuits that are the most difficult to eliminate. Imagine a high-frequency crystal oscillator (analog, but you can't avoid it). Now, for your VCO, imagine a variable-modulus counter and/or a pulse-dropping circuit, depending on your requirements. This is your new "VCO". The loop filter can now be done digitally.mit_mohit said:OK if a stictly digitalPLL is not available but can we think of some digital circuit which does the job of a PLL