[SI-LIST] Re: T-line resonant frequency
- From: "Landrum, Chris" <chris_landrum@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 27 Apr 2004 15:06:27 -0600
Micron has an app-note on their website for laying out point to point
DDR applications. They basically recommend a series terminating
resistor at the mid-point of the etch. The etch must be kept under 2
inches however. I have worked on a design using this approach and it
does work well. Of course, as Steve said, you should do the simulation
yourself. At any rate, take a look at the app note if you get a chance.
-----Original Message-----
From: steve weir [mailto:weirsp@xxxxxxxxxx]
Sent: Tuesday, April 27, 2004 5:02 PM
To: forsilist@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: T-line resonant frequency
Raj, sorry it took time to get back to you, but I think both Scott
and=20 Istvan have answered your question anyway. Your best bet with
DDR is to=20 keep the bus as short as practical. You mentioned
unterminated. You had=20 best simulate the heck out of that, as
unterminated DDR can be very=20 problematic.
Regards,
Steve
At 07:51 AM 4/27/2004 -0700, raj singh wrote:
>Steve, sorry for such a 'to the point' question.
> I should have been more descriptive....
>I have a DDR data driver to be used in point-to-point
>source terminated(unterminated) enviorment. I am using
>spice simulation to find out for what T-line delay
>driver gives worst jitter, rest all are fixed (PRBS,
>pkg parasitics, clk freq, Z0=3D50 ...etc). I am
>simulating just one driver.
> I found that it is not Td=3Dlambda,lambda/2,lambda/4
>which gives worst jitter, but values slightly less
>than this. WHY THIS? is what I want to clarify.
>
>Thanks
>Rjt
>
>--- raj singh <forsilist@xxxxxxxxx> wrote:
> > Hi all,
> >
> > What t-line delay (in terms clock period) will show
> > the worst driver jitter. Some papers, which i have
> > gone through, says it is when Td equals clock
> > period,
> > half the clock period or quarter the clock period
> > (calls it resonant frequency).
> > But cannot able to think of why is it so? Tried to devolope some
> > of my own ideas, but want to discuss with the list to get correct
> > answer.
> >
> > Thanks and regards,
> > Rjt
> >
> >
> >
> >
> >
> >
> > __________________________________
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