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Intel
®
820E Chipset
R
Design Guide 185
This design guide provides only examples. Many power distribution methods achieve similar results.
When deviating from these examples in any way, it is critical to consider the effects of the change.
In addition to the power planes provided by the ATX power supply, an instantly available Intel 820E
chipset-based system (using Suspend to RAM) requires that seven power planes be generated on the
board. The requirements for each power plane are documented in this section. In addition to on-board
voltage regulators, the Intel 820E chipset reference board has a 5 V dual switch.
5 V Dual Switch
This switch powers the 5 V dual plane from the 5 V core ATX supply during full-power operation.
During Suspend to RAM, the 5 V dual plane will be powered from the 5 V standby power supply. Note:
The voltage on the 5 V dual plane is not 5 V! The resistive drop through the 5 V dual switch must be
considered. Therefore, no components should be connected directly to the 5 V dual plane. On the ICH2
reference board, only the voltage regulators (for lower-voltage regulation) are connected to the 5 V dual
plane.
Note: This switch is not required in an Intel 820E chipset-based system that does not support Suspend to RAM
(STR).
VCCVID
This power plane is used to power the Intel PGA370 socket processor.
Refer to the latest revisions of the following documents:
• VRM 8.4 DC-DC Converter Design Guidelines
•
For the Intel 820E chipset/FC-PGA Vcc_vid requirements, refer to the Intel
®
820 Chipset Design
Guide Addendum for the Intel
®
Pentium
®
III Processor for the PGA370 Socket. These guidelines can
be downloaded from the Intel website at:
http://developer.intel.com/design/chipsets/designex/298178.htm
Note: This regulator is required in all designs.
VTT
This power plane is used to power the AGTL+ dual-ended termination and the 1.5 V power delivery to
the Intel PGA370 socket processor.
Refer to the latest revision of the following document:
• For the Intel 820E chipset/FC-PGA VTT requirements, refer to the Intel
®
820 Chipset Design Guide
Addendum for the Intel
®
Pentium
®
III Processor for the PGA370 Socket. These guidelines can be
downloaded from the Intel website at:
http://developer.intel.com/design/chipsets/designex/298178.htm
Note: This regulator is required in all designs.
VCC 2.5
The Pentium III processor for the Intel PGA370 socket does not use this signal.