Intel Xeon Processor Multiprocessor Platform Design Guide

88
Processor Power Distribution Guidelines
To satisfy damping requirements, total series resistance in the filter (from V
CC_CPU
to the top plate
of the capacitor) must be at least 0.35 Ω. It includes the DCR of the inductor and any resistance
(routing or discrete components) between V
CC_CPU
and capacitor top plate. Keep the routing short
and wide. If the total is less than 0.35 Ω, add a discrete resistor to make up the difference. For
example, if the selected filter inductor has a minimum of 0.1 Ω DCR, and a negligible routing
resistance (less than 10 mΩ), add a discrete resistor R
1
of approximately 0.3.Ω.
The total maximum resistance in each route cannot be more than 1.1 Ω as defined from V
CC_CPU
(more specifically, the baseboard via that connects the PLL filter to the V
CC_CPU
plane) to the
processor interposer pin. Refer to Figure 8-17 and Figure 8-18 for recommended filter circuits.
This path includes the total trace resistance (denoted “R-TRACE” in the following figures),
discrete resistor (if needed), inductor DCR, and Socket 603 resistance (0.025 Ω). It is important to
note that “R-TRACE” includes the total trace resistance between V
CC_CPU
and the processor
socket pin, but is represented in the figures as a single resistor to simplify the circuit representation.
Other routing requirements:
• C should be as close as possible to V
CCA
and V
SSA
pins in the socket (typically < 0.02 Ω per
route).
• Route away from clocks and fast switching signals
• V
CCA
route should be parallel and next to V
SSA
route (to minimize loop area)
• V
CCIOPLL
route should be parallel and next to V
SSA
route (to minimize loop area)
• L should be close to C; any routing resistance should be inserted between V
CC_CPU
and L
• Any discrete R should be inserted between V
CC_CPU
and L
Table 8-7. Component Recommendations - Capacitor
Part Number Value Tolerance ESL ESR
Kemet
T495D336M016AS
33 µF 20% 2.5 nH 0.225
Ω
AVX
TPSD336M020S0200
33 µF 20% TBD 0.2
Ω
Figure 8-17. Implementation 1 Using Discrete R
VCC
VCCA
VSSA
VCCIOPLL
L1/L2
L1/L2
C
C
Processor
PLL
R-Socket
603
R-Trace
R-Socket
603
R-Socket
603
R-Trace
Processor interposer "pin"
Baseboard v ia that connects
f ilt er to VCC plane
Trace < 0.02 Ω
Socket 603 pin