FreeLists / si-list / [SI-LIST] One clock or many, that is the question ?

["Steve Rogers" <SRogers@xxxxxxxxxxxxx>]

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

***********************************************************************

"This email and any attached files are confidential  and may be legally =
privileged.If you are not the addressee, any disclosure, =
reproduction,copying, distribution,, or other dissemination or use of =
this communication is strictly prohibited. If you have received this =
transmission in error please notify the sender immediately and then =
delete this email.

It is the policy of Micromill Electronics Limited that no legally =
binding statements, representations or commitments (collectively =
'statements') may be made by email. Any such statements must be =
confirmed either by facsimilie or by post before they will have legal =
effect. The sender of this email is not authorised to commit the company =
in any way and the addressee is hereby formally notified of that fact."

***********************************************************************




------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu