PLL vs DLL -> difference

[ivlsi]

Hi All,

What's the difference between PLL and DLL?

Is PLL an analog device while DLL is digital one?

Thank you!

 

[FvM]

I believe that the Wikipedia DLL article gives a good explanation
https://en.wikipedia.org/wiki/Delay-locked_loop

Another way to view the difference between a DLL and a PLL is that a DLL uses a variable phase (=delay) block where a PLL uses a variable frequency block.

In the Control Systems jargon, the DLL is a loop one step lower in order and in type with respect to the PLL, because it lacks the 1/s factor in the controlled block: the delay line has a transfer function phase-out/phase-in that is just a constant, the VCO transfer function is instead GVCO/s. In the comparison made in the previous sentences (that correspond to the figure where the integrator, and not the flat gain, is used), the DLL is a loop of 1st order and type 1 and the PLL of 2nd order and type 2. Without the integration of the error signal, the DLL would be 0th order and type 0 and the PLL 1st order and type 1.