Post subject: PLL's an more important Low pass folter
Posted: Thu Aug 09, 2007 2:27 am
Wed Sep 15, 2004 3:15 am
Location: Huntington beach
Well first i would like to know if anyone knows any online places
that have goos info on pll's? searching i only came up woth some very
basic stuff like wkipedia.
But my main question is on the after
the phase comparator the lpf (can this be a band pass?) and how exactly
does it effect settleing time. I would think a narrower bandiwidth will
lock loop faster since it would pass less noise. And i thought that
the filters job was just to pass dc because thats what input to the
varactor on the vco?
Sorry for the "newb" question but i actually
never seen a pll circuit, we use it internal to the chip so i cant probe
Post subject: Posted: Thu
Aug 09, 2007 5:39 am
Joined: Fri Feb 17,
2006 12:07 pm
Location: London UK
That site provides design guides and design routines for Mathcad
Hope it helps.
Post subject: Posted:
Thu Aug 09, 2007 10:36 am
Jun 27, 2005 2:02 pm
filter possible in PLL is a LPF. The purpose of the LPF is to smooth
the output of the FPD (Frequency Phase Detector) and it sets the speed
of the loop.
A wide filter will cause the loop to react faster,
since the filter's pole(s) is/are located far, therefore, the filter
has a wider reponse. The tradeoff, as you mentioned, will be a degradation
in phase noise and vice versa.
Post subject: Posted: Thu Aug 16, 2007 4:33 pm
Joined: Wed Sep 15, 2004 3:15 am
Thanks. i had not had the chance to thank you guys been doing
alot of reading.
I do understand pll better but not enough yet.