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TMDXSK437X: Design questions

Part Number: TMDXSK437X

I am using the AM437X Starter Kit as a basis for our design. There are some resistors that I am not sure what they do (EMC mitigation or timing?) and I would like to remove them if possible.

1) What is the purpose of the 0 ohm resistors in the DDR address and select lines (R98 – R121). Can I remove them?

2) What is the purpose of the 22 ohm resistors on the Ethernet Comm lines (R144 - R157). Can I remove them?

Thanks for your help.


  • 1. Yes, you can remove all these resistors. For DDR3 design refer to section in the AM437x Datasheet Rev. D. The Starter Kit employs a balanced-T topology, which is not recommended unless you have a lot of experience in DDR design and are able to perform SI analysis before committing to PCB.
    2. These resistors are required to avoid line ringing and should not be removed.
  • Hi Biser,

    Thank you for your reply.

    We are planning to start with the layout of the Starter Kit that is posted on your website and we will not touch the placement or routing of the DDR3 memory. I figured that was the safest and quickest way to get the board to come up the first time. We have no experience routing DDR memory, nor do we want to go through the the trials and tribulations of learning.

    We will be making changes with some of the peripherals, but we will not touch the core.

    Do you see any issues with using this approach?

    Thanks for your help,


  • Make sure you also maintain exactly the same PCB stack-up, to maintain the track impedances. Personally, I have used the same approach for an AM335x design and it worked perfectly.
  • Thank you Biser. We will be careful to duplicate the stack-up.