I guess it would depend not just on the peak voltage but on the energy in that peak (i.e. peak area). I don't know what technology the DSP is - overshoots like this should matter somewhere about 130 nm and below, if older, chances are you will face no problems (but we'll know for sure after several years :-). If 130 nm and below, it would really be an interesting experiment to have one board constantly on until it fails - after days, months or years ? Really interesting, if you make such an experiment please keep us posted. Dimiter ------------------------------------------------------ Dimiter Popoff Transgalactic Instruments http://www.tgi-sci.com ------------------------------------------------------ > -------Original Message------- > From: Mikhail Matusov <matusov@xxxxxxxxxxxx> > Subject: [SI-LIST] Effects of overshoot/undershoot on long-term reliability > Sent: Mar 03 '06 17:34 > > 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