Subject: DRAM output IV curves

From: "Edlund, Greg" <[email-masked]>
Date: Mon, 10 Feb 1997 10:27:38 -0500

Does anyone have experience trying to extract output IV curves from
DRAMs in the lab?  This seems like a tough nut to crack since DRAMs lose
their data unless you throw refresh patterns at them continuously.  I
haven't actually tried to do this myself, but I would guess you could
get the pull-down curve all right since the memory cells should default
to a zero state if you don't refresh them.  To get the pull-up curve,
you have to get your curve tracer to work in conjunction with a pattern
generator.

It sure would be nice to have some way of jamming the outputs to make
these measurements...

----------
Greg Edlund , Principal Engineer
Alpha Server Signal Integrity
Digital Equipment Corp.
129 Parker St. PKO3-1/20C
Maynard, MA 01754
(508) 493-4157 voice
(508) 493-0941 FAX
[email-masked]

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From: "D.C. Sessions" <[email-masked]>
Date: Mon, 10 Feb 1997 09:29:42 -0700

> It sure would be nice to have some way of jamming the outputs to make

First off, DRAM cells are read differentially and you can't count on
them degrading to all zeros.

As to the question, sure: write an all-ones or all-zeros pattern
to the DRAM (a counter works) and then read it out continually
(using the same counter).  Practically speaking, though, it might
be cheaper and quicker to just buy the model if the manufacturer
won't give you one.

Our experience (contact me directly, BTW; we're probably working
on at least one project in common) has been that several DRAM
makers can provide the models but aren't willing to publish
them -- strictly on a request basis.  I've gotten 24-hour turns
thanks to the clock skew between here and Asia.

-- 
D. C. Sessions
[email-masked]