DDR3 Placement and Routing Topology

[Anonymous_Ricky]

Hi all,

I am using DDR3 in Flyby Topology but due to space constarint in board I have to place my DDRs one over another.
What I need to know is can I place DDR3 in this way and have the connection of addr,command and control signals in star topology (like we do in DIMM modules) or do I need to maintain flyby topology for that. The addr, cmmd and cntrl lines are common for both DDRs only Data groups are different.

Regards,

Ricky

 

[cks3976]

For DDR-3 fly-by is the best layout architecture because this offers good noise margin to signals as compared to Tree or Star. But if this topology is tough to implement due to space constraints, you can consider using Daisy chain topology.

Please refer to following app notes for further reading:

http://cache.freescale.com/files/32bit/doc/app_note/AN3940.pdf
**broken link removed**

 

[robertferanec]

Hi Ricky, it depends on your design. I used DDR3 memory chips on top of each other - no problems. See my video about DDR3 layout at Altium Designer – DDR3 routing and PCB layout video