Re: DRAM output IV curves

Edlund, Greg wrote:
>
> 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...

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
dc.sessions@tempe.vlsi.com