96
Memory Controller
7.4.3.3
DDR 333 Embedded Address/Command/Control Routing Guidelines
This section lists the recommendations for the DDR 333 embedded address/command/control
signal routing (
RAS#
,
CAS#
,
WE#
,
BA[1:0]
,
MA[12:0]
,
CS[1:0]#
,
and
CKE[1:0]
). Refer to
for a block diagram of the lengths and matching requirements.
provides the guidelines from the register to SDRAM.
Table 51.
DDR 333 Embedded Address/Command Routing Recommendations (Sheet 1 of 2)
Parameter
Routing Guideline
Reference Plane
Route over unbroken ground plane
Preferred Topology
•
Micro-strip only for Un-buffered memory
configurations
•
Either Micro-strip or Stripline for Registered
memory implementations and lightly loaded
Un-buffered memory implementations (i.e. single
bank w/ less than or equal to 36pF input
capacitance).
Microstrip Trace 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
terminations.
•
>12 mils within group
•
>20 mils must be maintained from any other
groups (Clock/DQ/DQS)
Trace Length
Refer to following Embedded Addr/CMD Topology
for unbuffered and
for registered.
Series Resistor
22 +/- 5% ohms unbuffered configurations only
Parallel Resistor
51 +/- 5% ohms
•
Place the VTT terminations in VTT island after the
DIMM (trace length of 0.15” to 0.5”0.
•
Split termination of 100 ohms +/- 5% to 2.5 V and
100 ohms +/- 5% to ground
Package Trace Length:
Main Route Trace Lengths:
See Package Details for net length report
Refer to respective following Un-buffered or
Registered Topology/ Trace Length tables for more
details.
Summary of Contents for 80331
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