105
Memory Controller
Table 58.
DDRII 400 DIMM Source Synchronous Routing Recommendations
Parameter
Routing Guideline
Reference Plane
Layer
Route over unbroken ground plane
Strip line (layer 3 or layer 6)
Breakout
5 mils on 5 mils spacing. Maximum length of breakout
region can be up to 500 mils either microstrip or strip
line
Stripline Trace Impedance
Motherboard/Add-in Card Differential DQ
•
DQ signals: Single ended strip lines at 45 ohm
+/15% or 50 ohms +/- 15% impedance. Refer
Stripline Trace Impedance
Motherboard/Add-in Card Differential DQS
•
DQS Signals: Differential ended strip lines at
100ohm impedance. Refer to
and DIMM
DQS Topologies.
DQ Group Spacing (edge to edge)
•
Spacing same group: 12 mils minimum
•
Spacing from other DQ groups 20 mils minimum
•
For DQS from any other signals: 20 mils minimum
Overall Trace Length: 80331 signal Ball to DIMM
connector (no series connector)
2” minimum to 8” maximum (correlated with the clock
length from ball to DIMM).
DQS Length Matching:
•
Trace Length Matching within DQS group
•
Within one DQS pair plus and minus
•
All DQ/DQS lines with respect to the clock signal
+/-0.05” within DQS group
+/- 0.0250”
+/- 1” (target motherboard clock = +/- 1” of any
DQ/DQS pair)
Number of Vias
Two (for differential signals the number of vias on +
and - signals must be the same)
Routing Guideline
Route all data signals and their associated strobes on
the same layer.
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