[SI-LIST] Re: DDR DRAM
- From: "Ravinder Ajmani" <ajmani@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 7 May 2002 08:26:50 -0700
Hello SI-LISTers,
Thanks to all of you who replied to my post. A number of questions have
been raised and I wish to answer them.
1) I used HP 2.5 GHz probes with HP Infinium 1.5 GHz oscilloscope, using 8
GHz sampling rate.
2) I had gone through several Application Notes/other material and decided
to use source terminations because of the following constraints:
a) I do not have enough board space to provide parallel terminations or
both.
b) I am already exceeding our power budget, and can't afford the
additional current drain of parallel terminations.
c) The parallel termination used by me (on the failing bits only) were
selected by simulations and were also found to work on the actual card.
The problem as I see is that brand "X" DRAM puts data after the Strobe
(although still within their specs of 500 ps), whereas brand "Y" DRAM puts
data before the Strobe. Hence, I have a problem of matching my card layout
to work with both DRAMs.
Regards, Ravinder
PCB Development and Design Department
IBM Corporation
Email: ajmani@xxxxxxxxxx
***************************************************************************
Always do right. This will gratify some people and astonish the rest.
.... Mark Twain
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