Intel EP80579 Guide

Intel
®
EP80579 Integrated Processor Product Line May 2010
Order Number: 320068-005US 51
High-Speed Design Concerns—Intel
®
EP80579 Integrated Processor Product Line
5.5.5 Differential Clocking
Differential clocking requires the clock generator supply both clock and clock-bar
traces. Clock-bar has equal and opposite current as the primary clock and is also 180°
out of phase. To maximize the benefit of differential clocking, both clock lines must be
routed parallel to each other for their entire length. Devices connected to the clock
must also be designed to accept both the clock and clock-bar signals.
EMI reduction due to differential clocking is caused by H-field cancellation. Since H-field
orientation is generated by and is dependent upon current flow, two equal currents
flowing in opposite directions and 180° out of phase may have their H-fields cancelled
(see Figure 24). Lower H-fields may result in reduced EMI radiation.
Figure 23. Impact of Spread Spectrum Clocking on Radiated Emissions
Δ
SCC
non-SSC
(1-δ)f
nom
f
nom
Figure 24. Cancellation of H-fields Through Inverse Currents
CLK - clock trace
CLK' - clock bar
trace
H-field
caused by
Iclk
Iclk
Iclk'
H-field
caused by
Iclk'

Intel EP80579 Specifications

General

Brand	Intel
Model	EP80579
Category	Computer Hardware
Language	English