Power Plane Filter Requirements; Processor Vcca Decoupling Circuit Topology - Intel EP80579 Manual

System Power Delivery Guide—Intel
• Use bulk capacitors for the voltage regulator and multiple layer traces with heavy
copper to keep the parasitic resistance low. Use a minimum of three vias per
connection on each bulk capacitor.
• Place the top MOSFET drains as close to the VDC-input capacitors as possible.
• The sense resistor has to be wide enough to carry the full load current. A minimum
of 1 via per Amp to the Vcc plane must be used. Use more when space permits.
• Use solid 2 oz. copper fill under drain and source connections of the top and bottom
MOSFETs.
• The voltage regulator is usually left to the last moment. Often the allocated area is
a small, narrow strip and the location is poor. These factors combine so that the
design flow, described above, usually cannot be followed.
• General Rule: Copper fill is good. Fill the PCB with metal. There must be no large
areas of the board without metal. Increase the width of the grounds, V
power rails to fill any blank spots. Large metal fill areas allow the voltage regulator
to improve its heat radiation and thereby run cooler. Large copper fill areas have
other benefits too, including reducing series resistance and inductance and
capturing and dissipating RF energy by allowing eddy currents to flow.
6.6.3.6 IA-32 core PLL Power Delivery
6.6.3.6.1 Filter Specifications for VCCA
VCCA is a power source required by the IA-32 Processor core PLL clock generators.
Since this PLL is analog in nature, it requires a quiet power supply for minimum jitter.
Jitter is detrimental to the system; it degrades external I/O timings as well as internal
core timings (i.e., maximum frequency). Traditionally, this supply is low-pass filtered to
prevent any performance degradation. The IA-32 processor core has an internal PLL
super filter for the external 1.2V supply VCCA pin that dispenses with the need for any
external low-pass filtering. However, decoupling capacitors, two 0603 form factor
(0.1 µF), and one 1206 form factor (10 µF), must be placed as close as possible to the
VCCA pins. The decoupling topology is shown in
traces, circuits, and components are not shown in
Note: VCCA[1:2] pins are both connected to the Processor VCCA decoupling circuit.
Figure 46.

Processor VCCA Decoupling Circuit Topology

6.6.4

Power Plane Filter Requirements

Several power planes require very quiet supplies and also to generate a minimal
amount of noise. These supplies must have a filter to help reduce noise on the source
supply. Two types are power supply filtering are required:
®
Intel EP80579 Integrated Processor Product Line
Order Number: 320068-005US
®
EP80579 Integrated Processor Product Line
VCC (1.2V)
0 ohm (3A)
10 μf
10%
6.3V
Figure 46. Parasitics of connecting
Figure 46
. .
0 1 μf 0 1 μf
10% 10%
16V 16V
, and other
CC
EP80579
VCCA[1:2]
May 2010
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