Mikhail, I have read some specifications for Micron's transient limit's and I seem to remember they we're pretty high (around the 5v mark for a very limited time). We use Blackfin DSP's quite extensively over here and I know for a fact that ADI's own development kit's overshoot by the sort of numbers you describe. I tried getting a definitive answer from them but they are sticking to a standard 0.3v over/undershoot . I guess your answer really depends on how mission critical your design is and if you are running at temp extremes. Good Luck, Andrew -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Mikhail Matusov Sent: 03 March 2006 15:34 To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Effects of overshoot/undershoot on long-term reliability Dear experts, I designed a card based on the ADI TS201 TigerSHARC EZ-KIT evaluation board schematics. The TS201 has 2.5V 3.3V-tolerant I/Os . On this board it is directly connected to a 3.3V Micron SDRAM. Unfortunately, we had not simulated this interface before going into the layout. When we did we found that there is a huge overshoot on SDRAM read reaching almost 5V at the DSP pins. Our SI subcontractor recommends adding series terminations at the SDRAM pins. At this point it would mean major PCB redesign. I pulled an EZ-KIT card and captured the read cycle to verify the simulation results and found that the board behaves exactly as in simulation, i.e. the DSP chip is constantly subjected to this huge overshoot. However, the board works fine. So, I was wondering how I could estimate the risk of leaving the design as is? Thanks, ======================= Mikhail Matusov Hardware Design Engineer Square Peg Communications Tel.: +1 (613) 271-0044 ext.231 Fax: +1 (613) 271-3007 http://www.squarepeg.ca ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //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 ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //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