DDR3 Termination

[Nebruda]

Hi I have purchased a Zybo board for software development of my new project; I ask why in the schematic ( Rev B3) there are no termination resistors for DDR3, which I find rather on your ZedBoard ? Best regards. Nebruda

 

[elodg]

On the Zybo, a different routing topology has been used (tree vs. fly-by), that allowed for shorter traces and the use of near-series termination, instead of far-parallel.

[Nebruda]

Hi elodg,

I wish that the two DDR3 are mounted on the top side of the my PCB as ZedBoard; what  type of termination do you suggest? Parallel or series?

Thanks.

[elodg]

Although this is an old post, I would like to clarify the situation. @Nebruda, I see no reason to prefer DDR3 on a certain side from the user's point-of-view. Both topologies are technically sound and functionally the same. They present advantages and disadvantages for the board designer only. The tree topology on the Zybo allowed us to save a power supply, resulting in a more compact board. However, compared to the fly-by topology it is harder to route and validate.