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DDR clock lines

Dave Pulvermacher
Intellectual 870 points
Other Parts Discussed in Thread: AM3517

I just realized that my AM3517 board has a discrepancy compared to the EVM by logic PD.  On logics EVM both the CLK_DP and CLK_DN lines coming from the AM3517 go through a 10 ohm series resistor before reaching the DDR chips.  

I mistakingly routed the CLK_Dx lines over to the 2nd BEFORE the series resistors.  So this means that the first chip will will see CLK_Dx lines with a 10ohm resistor in series and the second won't.  

Are the 10 ohm resistors super important?  Or can I just put in 0 ohm?  I haven't yet looked to see if I can make board revs.  

  • 0
    TI__Guru* 89485 points

    There’s a good chance you will be able to get it to work by putting in the 0 ohm resistors, especially if you followed the routing guidelines in the datasheet (specifically, routing the differential pairs with 100ohm differential impedance, and following all of the skew mismatch guidelines).

     

    Regards,

    James