Cyril, everyone, In a past job at a test/consulting lab, I used modulated clocks with great success. They do not require respins and the differences in timing are typically (esp. at 66MHz) acceptable. This became one of the "quick & easy" fixes that we loved. These are not a solve-all solution though - if you have a failure margin of more than say 6dB you will probably have to do some board/sheilding work also to gain compliance. This technique is fairly widespread - my PC motherboard at home uses it (but like you mentioned, it is selectable in BIOS).
Con's????? None that I can think of, but...I have seen somewhere (maybe here??) that the EU is considering new regulations for modulated clocks, but this is in the early stages, so use them now while you can get the most benefit from them. Regards, Dave Heald "Binnom, Cyril A" wrote: > > Group, > > I am experiencing a EMI failure during testing and it has been isolated to > the processor board in which the fundamental frequency is 66.6 MHz the 3rd > harmonic that is our failure frequency is 199.8 MHz. We consulted the > manufacturer of the board and they have come up with a "spectrum spreading" > application for me to try. As I understand it, these type of applications > work by essentially jittering the clock frequency in order to spread the > energy over a wider band of frequencies. Thus the level at any particular > frequency is reduced even though the overall amount of energy radiated is > the same. The file they are sending me is a test application. If it works > well enough to get the unit to pass test, they have the ability to enable > the same application in the BIOS so it is always running. > > Does anyone have any experience using this type of application? Any opinions > on its validity? To those that can attest to its validity, any pros or cons > to the use of this application? > > Regards, > > Cyril A. Binnom Jr. > EMI/EMC Approvals Engineer > LXE, Inc. > (770) 447-4224 Ext. 3240 > (770) 447-6928 Fax > [email protected] > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
