Platform Power Delivery Guidelines
174
Design Guide
In addition, high-frequency decoupling may be required for signal integrity. System boards
designed using striplines with VCC_CPU and VSS references should not require high-frequency
decoupling beyond the recommendations listed in
. For systems using microstrip
configurations, a return path discontinuity will exist between the processor and the baseboard due
to the baseboard traces having only one reference plane. These systems should distribute
decoupling capacitors, as shown in
and described as follows:
•
4 minimum, 6 preferred 1 µF capacitors with 0805 packages distributed evenly over the data
lines.
•
3 minimum, 4 preferred 0.1 µF capacitors with 0805 packages distributed evenly over the
address and control lines.
Location of High-Frequency Decoupling
Place high-frequency decoupling as close to the power pins of the processor as physically possible.
Use both sides of the board if necessary for placing components to achieve the optimum proximity
to the power pins. This is vital because the inductance of the board's metal plane layers could
cancel the usefulness of these low inductance components.
Shorten the path from the capacitor pads to the pins that it is decoupling. If possible, place the vias
connecting to the planes within the pad of the capacitor. If this is not possible, keep the traces as
short and wide as is feasible. Possibly one or both ends of the capacitor can be connected directly to
the pins of the processor without the use of a via.
illustrates these concepts.
Figure 12-11. Decoupling Example for a Microstrip Baseboard Design
3-4 0.1 uF with 0805
body over the address
and control signals and
as close to the processor
package as possible.
4-6 0.1 uF with 0805
body over the data
signals and as close
to the processor
package as possible.
Data Pins
Address and
Control Pins
Cavity Under
Processor
Figure 12-12. 1206 Capacitor Pad and Via Layouts
Bad
Vias
Very Good
Pad
Capacitors
Good
Pin
Less Bad
Very Good
Summary of Contents for Xeon
Page 24: ...Introduction 24 Design Guide This page is intentionally left blank ...
Page 30: ...Component Quadrant Layout 30 Design Guide This page is intentionally left blank ...
Page 52: ...Platform Clock Routing Guidelines 52 Design Guide This page is intentionally left blank ...
Page 66: ...System Bus Routing Guidelines 66 Design Guide This page is intentionally left blank ...
Page 118: ...Intel 82870P2 P64H2 118 Design Guide This page is intentionally left blank ...
Page 146: ...I O Controller Hub 146 Design Guide This page is intentionally left blank ...
Page 148: ...Debug Port 148 Design Guide This page is intentionally left blank ...
Page 210: ...Schematic Checklist 210 Design Guide This page is intentionally left blank ...
Page 220: ...Layout Checklist 220 Design Guide This page is intentionally left blank ...
Page 222: ...Schematics 222 Design Guide This page is intentionally left blank ...