[SI-LIST] One clock or many, that is the question ?
- From: "Steve Rogers" <SRogers@xxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 7 Jan 2004 16:12:30 -0000
I am in the process of designing a bit of kit that has a USB 1.1 12 MHz =
speed hub and a number of USB to serial converter chips in. I am =
wondering which option would be best for clock distribution:-
Option 1. Put individual xtals on each chip
Option 2. Run one single clock which would then be buffered and =
distributed to each chip.
Having say a hex driver with 4 outputs swinging together at the same =
time is going to move a lot of fast current. I thought it might be good =
to split the clock to give two chips in phase and two anti-phase which =
might give a bit of cancellation of current.=20
The use of individual xtals obviously solves the problem of routing the =
clock around at the expense of a few more xtals but I think I just end =
up with more unpredictable but hopefully lower (on average) clock noise =
levels due to the non-phase locked nature of all the clocks?=20
Any advice?
Steve Rogers B.Eng (Hons) C.Eng IEE
RF Design Engineer
Micromill Electronics Limited
Leydene House
Waterberry Drive=20
Waterlooville Hampshire
PO7 7XX
Tel: +44 (0) 23 9236 6600
Fax: +44 (0) 23 9236 6673
Registered No. 1456922 (England). =20
Registered Office Brook Road
Wimborne, Dorset BH21 2BJ
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