Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel
®
Pentium
®
4 Processor-M and Intel
®
845MP/845MZ Chipset Platform
Design Guide 171
R
Figure 95. DDR Power Delivery Block Diagram
Vin Vout
Sense Adj.
Switching
Regulator
Vin Vout
Sense Adj.
Switching
Regulator
+
-
10K
10K
+V5
+VDDR2.5
+V5
+VDDR1.25
+
-
+VDDREF
11.7.1. DDR Memory Bypass Capacitor Guidelines
Discontinuities in the DDR signal return paths will occur when the signals transition between the
motherboard and the SO-DIMMs. To account for this ground to 2.5-V discontinuity a minimum of nine,
0603, 0.1-
µF, high-frequency bypass capacitors are required between the SO-DIMMs to help minimize
any anticipated return path discontinuities that will be created. The bypass capacitors should connect to
2.5 V and ground. The ground via should be placed as close to the ground pad as possible. The 2.5-V
trace should connect to a via that transitions to the 2.5-V copper flood and it should connect to the closet
2.5-V SO-DIMM pin on either the first or second SO-DIMM connector, with a wide trace. The
capacitors 2.5-V traces should be distributed as evenly as possible amongst the two SO-DIMMs. Finally,
the 2.5-V via should be placed as close to the 2.5-V pad as possible.
11.7.2. 2.5-V Power Delivery Guidelines
The 2.5-V power for the MCH-M system memory interface and the DDR-SO-DIMMs is delivered
around the DDR command, control, and clock signals. Special attention must be paid to the 2.5-V
copper flooding to ensure proper MCH-M and SO-DIMM power delivery. This 2.5-V flood must extend
from the MCH-M 2.5-V power vias all the way to the 2.5-V DDR voltage regulator and its bulk
capacitors, located at the end of the DDR channel beyond the second SO-DIMM connector. The 2.5-V
DDR voltage regulator must connect to the 2.5-V flood with a minimum of six vias, and the SO-DIMM
connector 2.5-V pins as well as the MCH-M 2.5-V power vias must connect to the 2.5-Vcopper flood.
The copper flooding to the MCH-M should include at least seven fingers to allow for the routing of the