[SI-LIST] Re: DDR1 without VTT termination

Hi Kathiresan,
I have designed two designs with single 32-bit DDR1 (160 MHz and 200 MHz). 
 It is possible to realize these designs without VTT termination, if the 
trace length is kept small (< 1.5"), and Half-strength drivers are used at 
the DRAM.  I used series terminations on the DDR side only, as my ASIC 
drivers are well behaved.  If your processor has impedance matched drivers 
and the trace length can be further minimized, then you may even be able 
to use the Weak drivers on the DRAM without using any terminations. 

The best way to find it out will be by running a simulation.

Regards, Ravinder
Server PCB Development
Hitachi Global Storage Technologies


Email: Ravinder.Ajmani@xxxxxxxxxxxxxx



"Kathiresan K" <k.kathir@xxxxxxxxx> 
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03/31/2008 07:18 AM

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[SI-LIST] DDR1 without VTT termination






Hi,
I need to have a single chip DDR1 (160 MHz, 16-Bit) memory for a 
processor.
I don't want to provide VTT terminations. I'll keep the trace length as
minimum as possible. I may provide series termination but I haven't done
pre-layout simulation yet.
Can somebody please clarify whether it can be designed without VTT
termination? If yes, what can be the maximum trace length I go for? If I'm
providing series termination, should I provide at both the ends for
bi-directional signals?

Regards,
Kathir


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