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7.5.2
DDRII-400 Trace Width/Impedance Requirements
The
Table 57
and add-in card eight layer PCB designs. Throughout this section the important recommendation to
meet is the trace impedance. The example in
Table 57.
Example Topology for DDRII Trace Width/Impedance Requirements
Topology
Microstrip
(layers 1 or 8)
Stripline
(layers 3 or 6)
NOTES:
1. Microstrip Differential Lines: Motherboard/Add-in 100 ohm: Constructed by two microstrips of 5 mils traces
separated by center to center distance of 13 mils refer to
2. Strip Differential Lines: Motherboard Stripline 100 ohms: Constructed by two striplines of 4 mils traces
separated by center to center distance of 12 mils refer to
3. Strip Differential Lines: Add-in stripline 100 ohms: Constructed by two striplines of 4 mils traces separated by
center to center distance of 13 mils refer to
below provides an example of a table of recommended topologies for motherboard
Min Trace
Trace Width
Spacing
(mils)
(mils)
5
5
7
12
6
12
4
12
5 (note 1)
20
5
5
6
12
5
12
7
12
6
12
4
12
4 (note 2)
20
5 (note 3)
20
Intel® 80331 I/O Processor Design Guide
Table 57
is provided as a reference.
Trace
Preferred
Impedance
signals
(ohms)
Breakout
Address/
45
CMD/Control
50
60
Differential
100 differential
Clock/DQS
Break out
45
DQ/CB
50
45
DQ/CB
50
60
Differential
100 Ohm
Clock/DQs
Differential
100 Ohm
Clock/DQs
Figure
35.
Figure
35.
Figure
35.
Memory Controller
Board Type
Motherboard/Add-in
Motherboard/Add-in
Motherboard/Add-in
Motherboard/Add-in
Motherboard/Add-in
Motherboard/Add-in
Motherboard
Add-in card
Add-in card
Add-in card
Add-in card
Motherboard*
Add-in card*
103
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