Power Delivery And Decoupling - Intel 855GME Design Manual

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Intel 855GME Chipset and Intel
inductance connections to the VCCA[3:0] pins due to the close proximity of the Layer 2 solid
ground plane 4 mils below the primary side 1.8 V flood. (Refer to the stack-up description in
Figure 140.)
VCCA0 capacitors are also placed on the primary side. No via is needed on the VCCA0 side of the
capacitors that connect to the VCCA0 pin. A small ground flood on the primary side shorts the
ground side of the 1206 form factor 10 µF VCCA0 decoupling capacitors via two ground stitching
vias to minimize interaction with Intel Pentium M/Celeron M processor FSB routing. The 0603
form factor 10 nF VCCA0 decoupling capacitor connects to internal ground planes through a
single ground stitching via.
VCCA1 decoupling capacitors are placed on the primary side on the bottom right corner of the
Intel Pentium M/Celeron M processor socket. No via is required to connect the VCCA1 side of the
decoupling capacitors to the VCCA1 pin. A small ground plane connects the groundside of the
1206 form factor 10 µF VCCA1 capacitors with a pair of vias to an internal ground plane. The
10 µF decoupling capacitor connects to internal ground planes through a single ground stitching
via.
The decoupling capacitors for VCCA2 are placed on the primary side on the right of the Intel
Pentium M/Celeron M processor socket. A small ground flood on the primary side is shared by the
GND-side of the two required decoupling capacitors for VCCA2. Both the 10 nF and the 10 µF
capacitor are placed in a vertical orientation on the primary side to avoid interaction with Intel
Pentium M/Celeron M processor FSB routing and do not require vias on the VCCA2 side to
connect to the VCCA2 pin.
Figure 41 depicts the Intel Pentium M/Celeron M processor 1.8 V Intel customer reference board
routing example.
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Figure 40. Intel Pentium

Power Delivery and Decoupling

LAYER 3 LAYER 3
1.8v from 1.8v from 1.8v from
Odem 855GME Odem
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6300ESB ICH Embedded Platform Design Guide
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M/Celeron M Processor 1.8-V VCCA[3:0] Recommended
GTLREF0 GTLREF0 GTLREF0
VCCA3 VCCA3 VCCA3
VCCA0 VCCA0 VCCA0
January 2007
PRIMARY SIDE PRIMARY SIDE
VCCA2 VCCA2 VCCA2
VCCA1 VCCA1 VCCA1
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