| Author |
Message |
ccw27
Joined: 13 Oct 2004
Posts: 292
Helped: 8
|
 28 Dec 2004 13:25 PLL versus multiple crystals |
|
|
|
Suppose your chip set needs multiple clocks for different circuitry. Why use a PLL and one crystal to generate different clock frequencies instead of using multiple crystals to do so?
Thanks
|
|
| Back to top |
|
 |
zorro
Joined: 06 Sep 2001
Posts: 327
Helped: 36
|
| 28 Dec 2004 14:14 PLL versus multiple crystals |
|
|
|
Deriving all the frequencies from a single source, the exact ratio between frequencies and the phase coherence are preserved.
Z
|
|
| Back to top |
|
|
radigital
Joined: 28 Dec 2004
Posts: 23
|
| 28 Dec 2004 17:44 Re: PLL versus multiple crystals |
|
|
|
Also multiple crystals would take up huge area on the PCB, and for some frequencies like
very high frequencies in the range of hundreds of MHz or GHz, crystal oscillators are not
available. But the most important reason is phase synchronisation between different parts of
the system.
|
|
| Back to top |
|
|
CDRCDR
Joined: 15 Feb 2004
Posts: 82
Helped: 2
|
| 30 Dec 2004 21:34 PLL versus multiple crystals |
|
|
|
| It is for phase synchronization,or else you will have phase offset between different Crystals even if you could install them on board.
|
|
| Back to top |
|
|
