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DM8168 DDR3 Routing

Shareef
Expert 1985 points

Hi All,

This post is regarding DM8168's DDR3 routing for top-bottom DDR placement.  We know that for Netra top bottom DDR3 placement is possible as per the DM8168 datasheet DDR routing guidelines. Due to very stringent constraints on the PCB dimensions, we want to go for top-bottom DDR placement. In this regard we have the following queries:

1.     Is it required to go for Micro-Via technology (blind or buried via) to achieve the same?
2.     Are there any specific routing guidelines apart from the ones mentioned in the DM8168 datasheet?
3.     What is the recommended board stack up for doing top bottom DDR routing?
4.     If this can be achieved in a conventional PCB (without use of Micro via) what is the recommended via size (drill, pad and anti-pad) to be used?

Regards,

Shareef

  • 0
    TI__Guru**** 393215 points
    Hi Shareef,
     
    There is a lot of information on DDR3 routing on the Internet. I would recommend you to check http://www.micron.com/products/support/technical-notes - there are quite a few technical notes on DDR3 there. There is no problem to use top-bottom placement, just try to follow the recommendations. As to microvia usage and stack-up, it's pretty much up to you. Depends on how much your design is cost-sensitive.
     
    Best Regards
    Biser
  • 0 in reply to Biser Gatchev-XID
    Expert 1985 points

    Hi Biser,

    Thanks for your response. We have done top bottom DDR3 placement for other processors. But in the case of 0.65mm BGA of DM8168 we cannot use a 8/18 via (8mil drill and 18mil pad) like for a conventional PCB. We have to go for lesser via dimension to avoid unnecessary cutting in the plane layers underneath the DM8168 processor (due to anti-pad clearance in plane layers). Hence we wanted to know what is the recommended board stack up, via size for DM8168's top-bottom DDR3 placement case? 

    Regards,

    Shareef.

  • 0 in reply to Shareef
    TI__Guru**** 393215 points
    Hi Shareef,
     
    Please note that the only DDR routing TI supports is the one provided in the DM816X DM, by following ALL of the guidelines in the data sheet.
     
    Best Regards
    Biser