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AM335x and DDR3 termination

Dharit Hothi
Prodigy 100 points
Other Parts Discussed in Thread: AM3352

Hello all,

Currently I am working on AM3352 processor and I want to use DDR3 RAM.

In datasheet of AM3352 in section 7.7.2.3 they are mentioning that if 16 bit DDR3 is used then termination is not mendetory.  Either we can use termination or we can make design without termination. 

So my question is if I am using 16 bit DDR3 then how can I make such design in PCB in which I can use DDR3 with termination and without termination also. 

I.E. as per datasheet in fig 7-47 & 7-48, If I am not using VTT termination then Can I make all Zo floating (refer figure 7-47)?

PCB routing Stub created in datalines before Zo can make any issue in in DDR3 communication? am3352.pdf

  • 0
    TI__Guru**** 393215 points
    Hi,

    You cannot have both on a single design. The stubs will definitely cause a problem. A typical DDR3 point-to-point topology may provide acceptable signal integrity without VTT termination, however system performance should be verified by performing signal integrity analysis using specific PCB design details before implementing this topology.

    If you do not have extensive experience in DDR layout design, I can suggest you take one of these two approaches:

    1. Make an exact copy of the Beaglebone Black DDR layout, including PCB stack-up. This is a proven point-to-point design. You can find the design files here: elinux.org/Beagleboard:BeagleBoneBlack

    2. Go for a design with VTT termination, following the layout guidelines from the AM335x Datasheet Rev. J.