89
Memory Controller
7.4.3
Embedded Configuration
The following tables provide layout guidelines for applications in which the DDR 333 memory
SDRAM components are placed directly on the board without a DIMM.
7.4.3.1
DDR 333 Source Synchronous Routine Guidelines
This section lists the recommendations for the DDR 333 embedded source synchronous routing.
These signals include all the DQ/DQS signals. Refer to
and
for the lengths and
matching requirements and
for the topology diagram. The topologies simulated are listed
in
Table 46.
DDR 333 Embedded Source Synchronous Routing Recommendations (Sheet 1 of 2)
Parameter
Routing Guideline
Reference Plane
Stripline routing: Route over unbroken ground plane
Micro-strip routing: Route over unbroken ground or
power plane
Preferred Topology
Stripline. Simulations show that stripline routing of the
DQ and DQS signals provides the best solution space.
Micro-strip routing is also acceptable.
Breakout Termination, Fan-in and Fanout width and
spacing
5 mils x 5 mils. Microstrip is recommended for pin
escapes and terminations.
Trace Impedance
•
45 ohm +/- 15% or
•
50 ohms +/- 15%
Trace Spacing (trace edge to edge)
•
5 mils is acceptable for pin escapes and
fan-in/fan-out from terminations.
•
>12 mils between any DQ/DQS signals
•
>20 mils bust be maintained from any other
groups
Package Trace Length:
The package lengths from Die to Ball provided in
must be accounted for when length
for more details on
segment lengths.
•
Breakout Trace Length (TL1)
≤
0.5”
•
Lead-in to Series Term. Trace Length (TL2)
1.0” to 4.0”
•
Fan-in/ Fan-out from Series Termination Trace
Length (TL3 & TL4)
≤
0.1”
•
Parallel Termination Trace Length (TL5)
0.15” to 0.5” (placed directly after series termination
fan-in)
•
Lead-in to SDRAM (TL6)
1.0” to 4.0”
Length Matching:
•
The package lengths from Die to Ball provided in
must be accounted for when length
matching.
•
With respect to the clock signal
•
When M_CK is routed on a stripline layer, DQS
should be routed to /- 1.5” of its
corresponding M_CK
•
When M_CK is routed on a micro-strip layer, DQS
should be routed to /- 1.0” of its
corresponding M_CK
•
Length Matching within DQS group
•
+/- .05” within DQS group
Series Termination
22 ohms +/- 5%
Summary of Contents for 80331
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