Hi Neven, I have not been able to establish a link between the DRAM vendor and higher EMI. In these cases the main source of emissions is the DRAM clock. I will suggest that you check the routing of the clock and also look for any overshoots. If there is sufficient timing margin then you should try increasing the source termination on the clock signal.
If you want to investigate the DRAM, then one way to find a quieter DRAM will be to check their IBIS models and select the one with the least drive strength. Regards, Ravinder Server PCB Development Hitachi Global Storage Technologies Email: [email protected] [email protected] Sent by: [email protected] 02/09/2007 01:19 PM To [email protected] cc Subject Best SDRAM for Low-Emission? Hello everyone, I have a 2-layer PCB design, plastic enclosure, using 120 MHz SDRAM, two stuffing options: 2MB (16 Mb) in 50-pin tsop package or 8MB (64 Mb) in 52-pin tsop. It is slightly above class B radiated emission at the multiples of 120 MHz. I troubleshot it and I determined the SDRAM is the only source of the failing frequencies, everything else is quiet. I wonder if anyone has looked in how various manufacturers' memory chips perform emission-wise, particularly the type that I am using. I hope to find a manufacturer who makes "quieter" modules, so I do not need to change anything else on my board. If anyone has done such a comparison/investigation, I would appreciate if you would be willing to share, on-line or off-line, the results - which memory/manufacturer works best EMI-wise in such conditions. Regards, Neven - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
