Working of a PLL

[shekhar_dandya]

Hi All,
Can anyone explain me how a PLL works and what is its basic aim?
Thanks
-Shekhar

 

[Kevin Weddle]

I think a PLL is basically just another circuit that is tapped in a location such that you can you can insert a signal or tap one. It's kind of like taking a signal from wherever else and inserting it harmlessly into another portion of the circuit. It's done all the time.

 

[ante1]

Hi shekhar,

Perhaps this might help: http://www.uoguelph.ca/~antoon/gadgets/pll/pll.html

 

[shekhar_dandya]

Thanx Ante.This was nice one to statr with.But I need still more understanding of the basics.I searched on google but did not find a satisfying article.
need more help
especially how it is used for FM detection etc,tone decoding..
-Shekhar

 

[audioguru2]

H Shekhar,
Experiment with a CD4046B PLL IC, a variable frequency clock oscillator and a CD4040B digital counter. Read their datasheets and try various combinations and you'll learn about PLLs quickly.

 

[Kevin Weddle]

A PLL has it's beginnings in the ideal situation of zero time difference. Although there is a feedback loop, there should be practically zero time difference. The voltage at the VCO is what's important. The signal takes the frequency up and the correction voltage from the phase comparator pulls that frequency somewhere close to the reference oscillator. Somewhere close is the key. The margin of error directly affects the ability to modulate. If it were perfect, then the output of the VCO would never change and your left with one frequency. But since there is a sizeable error, you have a change in frequency.

 

[nik2sonu]

can any one tell me how pll works with LM 567 IC

 

[audioguru2]

The datasheet for the LM567 explains how it works pretty well. There is an article about PLL's in our Articles section.