Intel 810A3, Design Manual

Page: 89 / 166

Intel
®
810A3 Chipset Design Guide 4-37
Layout and Routing Guidelines
from the filter inductor to the filter capacitor, and resistance of the associated vias. Part of this
resistance can be a physical resistor. A physical resistor may not be needed depending on the
resistance of the inductor and the routing/via resistance.
The filter capacitance should be chosen with as low of an ESR (equivalent series resistance) and
ESL (equivalent series inductance) as possible to achieve the best filter performance. The parasitics
of the filter capacitor can alter the characteristics of the filter significantly and even cause the filter
to be ineffective at the frequencies of interest. The LC filter must be simulated with all the
parasitics of the inductor, capacitor, and associated routing parasitics along with tolerances.
4.16.2 Recommended Routing/Component Placement
•
The filter capacitance should be placed as close to the VCCDA ball as possible so that the
routing resistance from the filter capacitor lead to the package VCCDA ball is < 0.1
Ω
.
•
The VSSDA ball should via straight down to the board ground plane.
•
The filter inductor should be placed in close proximity to the filter capacitor and any routing
resistance should be inserted between the board power plane connection and the filter inductor.
•
If a discrete resistor is used for the LC filter, the resistor should be placed between the board
power plane connection and the filter inductor.
4.16.3 Example LC Filter Components
Table 4-11 and Table 4-12 shows example LC components and resistance for the LC filter topology
shown in Figure 4-37 .
The resistance of the filter is defined as the total resistance from the board power plane to the filter
inductor. If a discrete resistor is used as part of this resistance, the tolerance and temperature
coefficient should be accounted for so that the maximum dc resistance in this path from the board
power plane connection to the DPLL VCCDA ball is less than 3.3
Ω
to meet the IR drop
requirement.
Table 4-11. DPLL LC Filter Component Example
Component Manufacturer Part No. Description
Capacitor KEMET T495D336MD16AS
33
µ
F ±20%, 16VDC,
ESR=0.225
Ω
@ 100 kHz, ESL=2.5 nH
Inductor muRATA LQG11A68NJ00
68 nH ±5%, 300 mA,
Max dc resistance = 0.8
Ω
, size=0603
Resistance — — < 3.3
Ω