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Difference Between a Pre-Scaler and Divider

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wchu01

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Would someone please enlighten what is the difference between a Pre-scaler and Divider within a Phase Locked Loop(PLL). As both are some form of divider then what is the need for a pre-scaler within a PLL.
 

sergio mariotti

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Both divide the input frequency.
But the user ask to the Prescaler to be the most "sensitive" as possible to low level signals.
Also prescalers sholud be clean and not back-inject interfering signals.
 

odyseus

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Also I think that prescalars have an analogue input and a digital output, while dividers are digital input & output??
Cheers
Ody
 

eltonjohn

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just to complement what has been said .. Prescalers migh have some input conditionning circuit either to square it ,amplify it or limite it .before it can be fed to the digital stage .The Digital stage is usually a high speed circuit !
 

bob_lv

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i think the output of the pll is often high frequency,normal divider can't work at this frequency,or power too much .so the prescaler is needed
 

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