116
Memory Controller
7.5.4.3
DDRII 400 Embedded Address/Command/Control Routing Guidelines
This section lists the recommendations for the DDR II 400 embedded address/command/control
signal routing. Refer to
,
and
for a block diagram of the
lengths and matching requirements.
Table 70.
DDRII 400 Embedded Address/Command/Control Routing Recommendations
Parameter
Routing Guideline
Reference Plane
Route over unbroken ground plane
Preferred Topology
Microstrip (outer layers) preferred
or
Stripline (inner layers)
Microstrip Trace Width and Spacing
5 mils x 5 mils. Microstrip is recommended only for pin
escapes and terminations.
Trace Impedance
45 ohms +/- 15%
or
50 ohms +/- 15%
Refer to Embedded Address/CMD topology
Microstrip Trace Spacing (edge to edge)
•
5 mils acceptable through pin field, break out
regions and terminations
•
>12 mils within group
•
>20 mils from any other clock/DQ/DQS groups.
Overall length 80331 signal Ball to register input
2” minimum - 10” maximum length matched /-
1.0” of target motherboard clock M_CK to PLL.
Series Termination
none
Parallel Termination
•
51 ohms, place the VTT terminations in the VTT
island after TL1 by trace length of TL10
•
or Split Termination of 100Ohms to 1.8V and 100
Ohms to Ground can be used
•
Place the VTT Terminations in VTT Island after
TL1 by Trace Length of TL10 (Single VTT
Termination)
•
Place Split terminations in respective Voltage rails
island.
•
Refer to Embedded Address/CMD Topology and
Table for Single VTT Termination or Split
Termination
Routing Guideline 1
Post register TL2-TL8 route as per JEDEC DDRII
Registered DIMM T routing.
Routing Guideline 2
3 Vias or less for preregister, route as per T routing
requirement for post register.
Содержание 80331
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