DM385, DM388
SPRS821D –MARCH 2013–REVISED DECEMBER 2013
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8.12.3.3 Step 3: Frequency-Domain Specification Guidelines
The PCB differential lines should be drawn in order to satisfy the Step 1 and Step 2 requirements.
However, although the PCB designer may draw the lines carefully, the lines can have poor electrical
performance due to many reasons.
Vertical connections such as vias and non-uniform line connections can degrade the electrical
performance of the differential lines. The ground design around the lines can also affect the electrical
performance. To ensure that the differential lines are well designed, the frequency-domain behavior must
be compared to the frequency-domain specification.
1. Intralane frequency-domain specification
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Differential-mode characteristics
Sdd12, Sdd11/Sdd22
Common-mode characteristics
Scc11/Scc22
Mode-conversion characteristics
Scd11, Scd12, Scd21, Scd22, Sdc11, Sdc12, Sdc21, Sdc22
2. Interlane frequency-domain specification
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Differential-mode characteristics
Sdd11/Sdd22
Common-mode characteristics
Scc11/Scc22
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Peripheral Information and Timings
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