What is the meaning of PLL Lock Range

[Gagan_SJSU]

PLL

Hi
What does it really mean when someone says that the PLL lock range is 47 Hz - 63 Hz? I was thinking that this should be related to the reference freq. which is usually in KHz-MHz range. But as this is in Hz so I am very confused. Does it mean that the reference freq. will be between 47 Hz - 63 Hz and my PLL should lock on to this. But I really do not think so. Can someone please explain.
Thanks

 

[srizbf]

Re: PLL

if pll ref freq is assumed to be 'f' Hz,
then lock range of 47-63Hz means

the system will faithfully follow even if input frequency varies that much
on either side.

srizbf
24thjune2010

 

[Gagan_SJSU]

Re: PLL

Thanks for your reply

So does it means my reference freq. has to fall somewhere between this range and will be in Hz. This PLL is a part of a bigger microprocessor so would not it be too slow if this would be the explanation. Lets say my Fref is 55 Hz so what would be the PLL lock range according to your explanation.

 

[srizbf]

Re: PLL

Lock Range is the range of frequencies in the vicinity of fo (where fo is the VCO frequency), over which the PLL can maintain lock with an input signal.

your query can be seen in the above context.

hope it gets you to somewhere closer.

srizbf
24thjune2010

 

[LvW]

Re: PLL

I suppose we should discriminate between pull-in-range, lock-range and hold-range.
I know, that sometimes different terms are used, however, according to my understanding the following definition applies:
The lock range is the frequency range around the nominal VCO frequency in which the loop can acquire lock within one cycle.
This is in contrast to the hold range which is identical to the definition as described in the former reply.

 

[Gagan_SJSU]

Thanks Everyone....Can you please provide me some numerical figures to get a better understanding. With 47 Hz - 63 Hz as the locking range, can you site a VCO center freq and then in that CF and this lock range context, what would be the max. and min. frequencies that the PLL would be able to lock