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why does the ferrite beads be abnegated in hawkboard OMAP-L138EVM

xunliang ma
Intellectual 315 points
Other Parts Discussed in Thread: OMAP-L138

hello all

      my board was designed refering to the hawkboard OMAP-L138EVM, and in the letter <Hawkboard Issues - TI Annoucement> , i know that it has many issues. by visiting the hawkboard website, i find that it modify the two ferrite beads in the DDR2 power system. as the figure below

it  saids: "The fix is made up by removing two ferrite beads and shortening the pads afterwards",  and the schematic is as below

and my question is , why delete the two ferrite beads and short the pads?

     now my board has problem and i doult that is has relationship with the DDR2.  if i hold the beads on my board, i can use the DDR2 to write the UBL to nandflash, but when i write the UBOOT or kernel, it will become unsteadiness, and always stop when booting.

     and if i delete the two beads, i can't use the DDR2 to write the UBL to nandflash, it will be stop when writing on 0%,  but i can use the common memery on my OMAP-L138 to write the UBL to nandflash. so i doult that is has the issue with the DDR2.

     then, i  attempted  to  write or read the DDR2 alone with CCS4.2 ,  and i found that it was no bad, i  can do it well. so i doult that the problem above is the problem with ferrite beads, and who can tell me why the hawkboard delete the two beads?

thank you!

  • 0
    Expert 1950 points

    Hello,

    You can find information in hawkboard google group, search for quite old "hawkboard hardware lite analysis" topic.

    Jakez

  • 0 in reply to Jakez
    Intellectual 315 points

    thank you jakez

               i have read the <HAWKBOARD rev.A HARDWARE LITE ANALYSIS> you writen, and i know that it is the problem with the noise on the groud of DDR2 chip, but although i have attempt all ways you have mentioned, it has no use.

              i have two boards, one has works well by short FB12 and FB13. but the other is bad, which i have described above, the two boards has the same circuits and route and chips on it , now i don't know how to do yet.

         and thank you again.

    xunliang