[SI-LIST] Re: Effects of overshoot/undershoot on long-term reliability
- From: "Dimiter Popoff" <dp@xxxxxxxxxxx>
- To: <matusov@xxxxxxxxxxxx>
- Date: Fri, 03 Mar 2006 17:42:00 +0200
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
>
>
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