[SI-LIST] Re: DDR3 Vref and Vtt plane
- From: Chockalingam Selvaraj <chockalingam.s@xxxxxxx>
- To: 陶冶 <taoye000@xxxxxxxxx>, qantrix <qantrix@xxxxxxxxx>
- Date: Sun, 5 Dec 2010 11:23:15 +0530
Hi Deepak,
Vref is supposed to track the variations in the 1.5V plane feeding the DDR2
circuits.
Hence, having a R-divider close to the Vref pin will help.
If you are having 3 separate supplies for the 3 circuits, then Vref has to be
from the corresponding 1.5V
By the way, what do you mean by robust results? Any particular issue in your
current board?
Thanks and regards
Chockalingam.S (Ck)
________________________________________
From: si-list-bounce@xxxxxxxxxxxxx [si-list-bounce@xxxxxxxxxxxxx] On Behalf Of
陶冶 [taoye000@xxxxxxxxx]
Sent: Saturday, December 04, 2010 11:29 PM
To: qantrix
Cc: Jia Liu; deepak Engineer; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDR3 Vref and Vtt plane
Hi Deepak,
I think it is not necessary to use a regulator, In DDR3,Vref is very
important,u can get it with two resistance.this voltage's tolerance is
+/-15mv£¬if possible u can around it with GND.In short£¬layout is very
important£¬be carefully.
2010/12/3 qantrix <qantrix@xxxxxxxxx>
> How you would place decoup caps in double sided scenario?
> 2010/10/19 Jia Liu <liujia.scu@xxxxxxxxx>
>
> > Hi Deepak,
> > I think your plan is good.
> > Maybe you can employ the double-side mount ddr chips for the 4 chips
> 800Mhz
> > and 2 chips 667MHz to save PCB space.
> >
> > Br/Jia
> >
> > 2010/10/18 deepak Engineer <deepaksiengg@xxxxxxxxx>
> >
> > > Hello Experts,
> > > In my design we have three processor with 3 DDR3 interface.
> > > This DDR3 interface are working on 800MHz and 667Mhz.
> > >
> > > upto now, i was using a voltage divider for Vref and independant Vtt
> > plane.
> > >
> > > but now I am planning to do some changes to get a robust results.
> > >
> > > 1. planning to use a regulator for Vref
> > > 2. may be a common Vtt plane for all three memory interface.
> > >
> > > would you suggest on how can I reduce the PCB space and components ??
> > > memory #device speed
> > > DDR3 4 800MHz
> > > DDR3 2 667MH
> > > DDR3 1 667MHZ
> > >
> > > Deepak
> > >
> > >
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