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AM3517 DDR2 DQS DQ routing the same trace length with series resistor?

YanChang Liang
Prodigy 70 points
Other Parts Discussed in Thread: AM3517

hi,

    i'm routing AM3517 ZER package.

    the DDR2 is 32bit,that is 4bytes,and there are series resistor on DQSx   /DQSx  (x=0/1/2/3),but all DQx (x=0---31) does not has series resistor.

    since DQSx should be route the same trace length as DQ,how about the series resistor? when  calculate the length of DQS,does it's two pad length should be add?why or why not?

    CPU'pad---->Top trace ---> series resistor--->top trace -->  via ----> inner layer trace -->  via --->top trace --->ddr2 chip' pad

  • 0
    TI__Genius 9190 points

    Hello,

    when calculating the length, you will need to add the length of the resistor, not the lenght of the pads.  the signal must travel the entire length of the resistor, so you want to make sure that the overall lengths are the same for both the DQ and DQS lines.