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

1.3.3. Edge Coupling

Consider two differential pairs routed on the same signal layer as shown in Figure 1 with a height (H) from the reference plane.

Table 6.   Microstrip NEXT vs. Aggressor Separation Microstrip routing requires a separation of 6H and 7H to properly manage the crosstalk coupling to less than 1% for NEXT and FEXT, respectively. However, to achieve 1% of crosstalk coupling using stripline routing, requires only 5H separation for NEXT and 2H separation for FEXT.
Separation (D) Isolation (dB) Coupled Voltage from a 1-V Aggressor (mV) Coupling (%)
1H 22 79 7.9
2H 27 45 4.5
3H 31 28 2.8
4H 35 18 1.8
5H 36 16 1.6
6H 41 9 0.09
Table 7.   Microstrip FEXT vs. Aggressor Separation Microstrip routing requires a separation of 6H and 7H to properly manage the crosstalk coupling to less than 1% for NEXT and FEXT, respectively. However, to achieve 1% of crosstalk coupling using stripline routing, requires only 5H separation for NEXT and 2H separation for FEXT.
Separation (D) Isolation (dB) Coupled Voltage from a 1-V Aggressor (mV) Coupling (%)
6H 34 20 2.0
7H 41 9 0.09
Table 8.   Stripline NEXT vs. Aggressor Separation
Separation (D) Isolation (dB) Coupled Voltage from a 1-V Aggressor (mV) Coupling (%)
1H 24 63 6.3
2H 32 25 2.5
3H 36 16 1.5
4H 39 11 1.1
5H 40 10 1.0
Table 9.   Stripline FEXT vs. Aggressor Separation
Separation (D) Isolation (dB) Coupled Voltage from a 1-V Aggressor (mV) Coupling (%)
1H 32 25 2.5
2H 40 10 1.0
Note: Use stripline routing to avoid FEXT concerns. Use stripline traces with 5H differential pair-to-pair separation to minimize NEXT to 1%.
Note: If microstrip routing is required, used 6H-7H differential pair-to-pair separation to avoid NEXT and FEXT issues.
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