108
Memory Controller
7.5.3.3
DDRII 400 Address/Command/Control Routing Guidelines
This section lists the recommendations for the DDR II 400 Address/Command and Control signals
(
RAS#
,
CAS#
,
WE#
,
BA[1:0]
,
MA[12:0]
,
CS[1:0]#
, and
CKE[1:0]
for a description of the segment lengths and matching requirements.
Table 63.
DDRII 400 DIMM Address/Command/Control Routing Recommendation
Parameter
Routing Guideline
Reference Plane
Route over unbroken power plane
Preferred Topology
Microstrip lines
Breakout Trace Width and spacing
5 mils x 5mils.
Trace Spacing
•
5 mils acceptable between the pins and the
breakout regions.
•
>12 mils within group
•
>20 mils from any other clock/DQ/DQS groups.
Trace Impedance
45 ohms +/- 15% or 50 ohms +/- 15%
Trace Length: Overall length from 80331 signal Ball to
DIMM Connector
2.0”min to 10” max (Correlated with in +/- 1” of
DQ/DQS and command lead-in MB length)
Refer to following table for segment lengths.
Length Matching Requirements:
2”-10” matched /- 1” of target motherboard
M_CK
Single Parallel Termination
Split Termination
51 ohms +/- 5% to VTT
100 ohms +/- 5% to ground and 100 ohms to 1.8V
Routing Guideline 1
Route clock signal as differential pair with target
differential impedance of 100 ohms
Routing Guideline 2
Place the VTT terminations in the VTT island after the
DIMM with a trace length of 0.15” to 0.5”
Routing Guideline 3
For split terminations place the VTT termination in
their respective power islands
Number of vias
2 Vias or less
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