[SI-LIST] Re: What if DDR termination power Vtt cannot sink current.
- From: "Ferhat Yaldiz" <ferhat.yaldiz@xxxxxxxxxxxxxx>
- To: "'Han Li'" <jasonleehan@xxxxxxxxx>, "'SI LIST'" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 21 Aug 2008 12:53:41 +0300
Hi Li,
You must guarantee necessary high current in DDR SDRAM Vtt design. Use
strong switching power supplies, since sink and source currents (current
consumptions) are very high. If your DDR SDRAM is 72-bits, you can think
max.
current is 2.5A-3A. You must be careful to maintain smaller 40mV from vtt.
If your power supply does not obtain necessary current, You must be worry.
Because, Signal quality changes,Overshoot and undershoot increases, noise
margins decreases. And this instability of power reflected timing skews. And
Vtt design I recommend to you :
- close switching power supplies to vtt islands. (reduce impedance)
- wide vtt island to carry high current.
- do not cross layers (only top layers)
And you can check Micron and Samsung App.notes.
Best Regards,
FERHAT YALDIZ
HARDWARE DESIGN ENG.
TUBITAK-ITI
TURKIYE
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Han Li
Sent: Thursday, August 21, 2008 10:19 AM
To: SI LIST
Subject: [SI-LIST] What if DDR termination power Vtt cannot sink current.
Hello, experts,
1.25V DDR termination power Vtt should both sink and source
current. I wondered what happened if such a power cannot sink current? What
effects would this on DDR chip and on Power-Manangment IC? Could anyone
kindly provide some advices, research papers or reports on this?
Thank you very much.
--
Best Regards
Li Han
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