What causes phase shifting in a PLL output?

[watertreader]

Hi,

May I know what kind of problem would cause phase shifting in a PLL output? The output of the PLL always shift with respect to the Local oscillator signal

Thanks

 

[FvM]

phase shifting

It's present by design of the PLL, depending on the involved phase detector. The usual analog phase detector gives a 90° phase shift.

 

[watertreader]

site:www.edaboard.com pll

Hi,

The amount of phase shift varies a with time...though the output frequency remains constant....

does not sound like the constant phase shift you have mentioned

 

[biff44]

pll for phase shifting

Because you give us so little knowledge (pll part number, frequencies, divisor ratios,etc), you can not expect an accurate answer.

 

[LvW]

phase shift pll

Hi,

The amount of phase shift varies a with time...though the output frequency remains constant....
does not sound like the constant phase shift you have mentioned

"constant" can only mean "nearly constant" because - as a result of feedback action - the phase shift must swing around the target of 90 deg by a small amount which depends on the loop gain.
Therefore my question: How large is the unwanted phase shift ? Constant or not ?