21
EVA-X4300 System Design Guide
Chapter 2
Layout
Guide
7.
Avoid running PCI clocks in parallel with other signals for a long distance, for
interference and coupling.
8.
The user may need to drive two or more source-terminated clock lines with sin-
gle output. However, the following condition must be achieved:
i. The clock traces length must be as equal as possible, to guarantee the arriv-
ing time of the reflected pulses.
ii. The loads must be balanced, to guarantee the same shape of the reflected
pulses.
iii. The termination value must be calculated according to:
R
t
= Z
0
– R
s
* N
R
t
= termination resistor,
Ω
R
s
= output impedance of the driver
Z
0
= line impedance
N = number of lines
2.10
USB 2.0
1.
Route the Hi-Speed USB differential pairs over continuous ground or
power planes. Avoid crossing anti-etch areas and any breaks in the inter-
nal planes (plane splits).
2.
Avoid placing a series of vias near the DP and DM lines, as these will create
“break areas” in the ground plane below.
3.
Avoid routing the USB differential pairs near I/O connectors, signal headers,
crystals/ oscillators, magnetic and power connectors.
4.
Maintain parallelism between USB differential signals, with the trace spacing
needed to achieve
90
Ω
differential impedance
.
5.
We recommend the trace
Width/ Spacing/ Isolation
of USB differential pairs to
be
8 mil/ 8 mil/ >20 mil
. And the mismatch of the differential pairs should be
less than ±70 mil
. These values may vary depending on the actual PCB
parameters.
6.
The maximum trace
length
of USB differential pairs should be
less than 2”
.
Summary of Contents for EVA-X4300
Page 1: ...User Manual EVA X4300 System Design Guide ...
Page 4: ...EVA X4300 System Design Guide iv ...
Page 5: ...Chapter 1 1 Overview ...
Page 7: ...Chapter 2 2 Layout Guide ...
Page 10: ...EVA X4300 System Design Guide 6 2 2 Package Outline ...
Page 11: ...7 EVA X4300 System Design Guide Chapter 2 Layout Guide ...
Page 32: ...EVA X4300 System Design Guide 28 ...
Page 33: ...Appendix A A References ...
Page 35: ...31 EVA X4300 System Design Guide Appendix A References ...