Specifications

Ref# 420826 Intel
®
Atom™ processor CE4100 95
Platform Design Guide
Intel Confidential
8.2.1.1 USB 2.0 Trace Separation
Use the following separation guidelines.
• Maintain parallelism between USB differential signals with the trace spacing needed to
achieve 90-Ω differential impedance. Deviations will normally occur due to package
breakout and routing to connector pins. Just ensure the amount and length of the
deviations is kept to the minimum possible.
• Use an impedance calculator to determine the trace width and spacing required for the
specific board stack-up being used. 4-mil traces with 4-mil spacing results in
approximately 90 Ω differential trace impedance.
• Minimize the length of high-speed clock and periodic signal traces that run parallel to
high-speed USB signal lines, to minimize crosstalk. Based on EMI testing experience, the
minimum suggested spacing to clock signals is 50 mils.
• Based on simulation data, use 20-mil minimum spacing between high-speed USB signal
pairs and use other signal traces for optimal signal quality. This helps to prevent
crosstalk.
Figure 8-6. Recommended USB Trace Spacing