AN 672: Transceiver Link Design Guidelines for High-Gbps Data Rate Transmission

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ID 683624
Date 1/29/2020
Public
Document Table of Contents
Document Table of Contents x
1. AN 672: Transceiver Link Design Guidelines for High-Gbps Data Rate Transmission
1. AN 672: Transceiver Link Design Guidelines for High-Gbps Data Rate Transmission x
1.1. PCB Material Selection 1.2. Stackup Design 1.3. Channel Design 1.4. Summary 1.5. Document Revision History for the AN 672: Transceiver Link Design Guidelines for High-Gbps Data Rate Transmission
1.1. PCB Material Selection x
1.1.1. Loss Tangent and Dissipation Factor 1.1.2. Dielectric Constant 1.1.3. Fiberglass Weave 1.1.4. Copper Surface Roughness
1.3. Channel Design x
1.3.1. BGA Channel Breakout 1.3.2. Channel Routing Design 1.3.3. Edge Coupling 1.3.4. Broadside Coupling 1.3.5. Transparent Via Design 1.3.6. Blocking Cap Optimization 1.3.7. Connectors Optimization
1.3.2. Channel Routing Design x
1.3.2.1. Trace Width Selection 1.3.2.2. Loose vs. Tight Coupled Traces 1.3.2.3. Crosstalk Control
1.4. Summary x
1.4.1. PCB Material Selection 1.4.2. Stackup Design 1.4.3. Channel Design 1.4.4. References
1. AN 672: Transceiver Link Design Guidelines for High-Gbps Data Rate Transmission

1.3.2.1. Trace Width Selection

PCBs are becoming very constrained, and using fine trace widths down to 4 mils wide is commonly used to improve routability. However, for high-speed signals, narrow trace geometries increases conductor loss due to skin effect. As a result, routabilty must be properly balanced with trace width selection for better performance. Larger signal attenuation occurs for signals at 4 mils vs. 5 to 6 mils. For example, for a 28-Gbps signal, the difference in attenuation at the Nyquist frequency (14 MHz) is approximately 3 dB for 4 mils versus 6 mils wide trace.

Figure 15. Trace Width vs. Signal Attenuation

Trace Width vs. Signal Attenuation

Note: For high-speed transceiver signals, use trace widths of 6 mils or more to reduce conductor loss.
Note: Limit the use of 4 mil trace widths to the BGA breakout area and keep their trace length as short as possible.
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