Someone told me that I can use the phase detector of a PLL to implement a phase detector. I tried understanding the circuit to this end, but could not figure out to use the phase detector inside the PLL.
With only the information given, I would guess that the idea was to use the PLL as a d(phi) to voltage converter. A pll could perhaps do this, since in many cases, the operate a VCO. You could perhaps measure the voltage driving the VCO. But my guess would be that you actually need to have the analog loop complete for this to work. I cannot otherwise understand how this might work.