103
Memory Controller
7.5.2
DDRII-400 Trace Width/Impedance Requirements
The
below provides an example of a table of recommended topologies for motherboard
and add-in card eight layer PCB designs. Throughout this section the important recommendation to
meet is the trace impedance. The example in
is provided as a reference.
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
Table 57.
Example Topology for DDRII Trace Width/Impedance Requirements
Topology
Trace Width
(mils)
Min Trace
Spacing
(mils)
Trace
Impedance
(ohms)
Preferred
signals
Board Type
Microstrip
(layers 1 or 8)
5
5
Breakout
Motherboard/Add-in
7
12
45
Address/
CMD/Control
Motherboard/Add-in
6
12
50
Motherboard/Add-in
4
12
60
Motherboard/Add-in
5 (note 1)
20
100 differential
Differential
Clock/DQS
Motherboard/Add-in
Stripline
(layers 3 or 6)
5
5
Break out
Motherboard/Add-in
6
12
45
DQ/CB
Motherboard
5
12
50
Add-in card
7
12
45
DQ/CB
Add-in card
6
12
50
Add-in card
4
12
60
Add-in card
4 (note 2)
20
100 Ohm
Differential
Clock/DQs
Motherboard*
5 (note 3)
20
100 Ohm
Differential
Clock/DQs
Add-in card*
Содержание 80331
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