In high-speed differential serial data transmission (such as PCIe, SATA, and USB 3.0), why are signal traces routed in closely spaced parallel pairs?
Answer and explanation
Correct answer: A. To cancel external noise by measuring the voltage difference between two inverted lines
- Step 1: High-frequency signals radiated through circuit traces are susceptible to electromagnetic interference (EMI) and crosstalk.
- Step 2: Differential signaling sends equal and opposite voltage waveforms ( and ) down adjacent traces; because external noise impacts both traces equally, the differential receiver subtracts them, canceling the common-mode noise.
Answer
To cancel external electromagnetic interference (noise) by measuring the voltage difference between the two inverted lines
Why not the others: 'To double the electrical current carrying capacity for device charging' Power delivery traces are made wider to carry current, whereas paired differential signals carry low-power data; 'To allow one wire to transmit data while the other wire provides ground reference' Single-ended signaling uses a ground reference wire, whereas differential signaling compares two inverted signal lines; 'To store backup copies of transmitted bits in case of wire severance' Differential pairs do not provide redundant storage; both wires are required to reconstruct each bit.
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