Intel Xeon User Manual

Platform Power Delivery Guidelines
172 Design Guide
To satisfy damping requirements, total series resistance in the filter (from VCC_CPU to the top
plate of the capacitor) must be at least 0.35 Ω. This includes the DCR of the inductor and any
resistance (routing or discrete components) between VCC_CPU and capacitor top plate. Keep the
routing short and wide. If the total is less than 0.35Ω, 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 of approximately 0.3 Ω. The
total maximum resistance in each route cannot be more than 1.1 Ω as measured from VCC_CPU
(the baseboard via that connects the PLL filter to the VCC_CPU plane) to the processor interposer
pin. It is important to keep the total resistance of each of the PLL filter circuits on the motherboard
no larger than necessary. Figure 12-9 and Figure 12-10 illustrate the recommended filter circuit.
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 VCC 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 VCCA and VSSA pins in the socket (typically < 0.02 Ω per
route).
• Route away from clocks and fast switching signals.
• VCCA route should be parallel and next to VSSA route (to minimize loop area).
• VCCIOPLL route should be parallel and next to VSSA route (to minimize loop area).
• L should be close to C; any routing resistance should be inserted between VCC_CPU and L.
• Any discrete R (if needed to meet minimum resistance) should be inserted between VCC_CPU
and L.
Figure 12-9. Filter Implementation 1: Using Discrete Resistor
Figure 12-10. Filter Implementation 2: No Discrete Resistor
VCC_CPU
VCCA
VSSA
VCCIOPLL
L
C
C
Processor
PLL
R-Trace
Processor Interposer "Pin"
Trace < 0.02 Ω
Socket 603 Pin
Baseboard Via that
Connects Filter to
VCC_CPU Plane
R-Socket
603
R-Socket
603
R-Socket
603
Discrete
Resistor
R-Trace
Discrete
Resistor
L
VCC_CPU
VCCA
VSSA
VCCIOPLL
L
C
C
Processor
PLL
R-Trace
Processor Interposer "Pin"
Trace < 0.02 Ω
Socket 603 Pin
Baseboard Via that
Connects Filter to
VCC_CPU Plane
R-Socket
603
R-Socket
603
R-Socket
603
R-Trace
L

Intel Xeon Specifications

General

Brand	Intel
Model	Xeon
Category	Processor
Language	English