The following are some basic requirements for USB 3.0 cables:
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Signal line structure:
In addition to the original power line and data lines (D+, D−) of USB 2.0, USB 3.0 cables add four additional high-speed data channels to form two SuperSpeed differential pairs (RX1+/RX1− and TX+/TX−), supporting full-duplex data transmission up to 5 Gbps. -
Materials and Quality:
- The conductor material should be high-quality copper wire, such as oxygen-free copper, to ensure low resistance and clear signal transmission.
- The insulating material should meet specific dielectric constant and dielectric loss requirements to minimize signal attenuation and delay. Typically, materials with a low dielectric constant (DK) are preferred.
- The shielding layer must be sufficiently tight to reduce electromagnetic interference (EMI) and signal crosstalk. This usually includes one or two layers of metal foil shielding, plus a ground-braided layer.
- Wire color: According to the USB 3.0 standard, the internal SuperSpeed differential pair must be blue to distinguish it from the outer jacket of the cable. This serves as a unique identifier for USB 3.0.
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Length Limit:
The USB 3.0 standard does not specify a strict maximum cable length. However, due to the effects of signal attenuation and noise, it is generally recommended in practical engineering applications that the cable length be kept under 3 meters, as exceeding this may affect data transmission rate and stability. -
Interface Compatibility:
The USB connectors at both ends of the cable must comply with the USB 3.0 interface standard to ensure physical compatibility with USB 3.0 devices, while also maintaining backward compatibility with USB 2.0 devices. -
Electrical Performance:
The cable must undergo rigorous electrical performance testing, including signal integrity and consistency verification, to ensure compliance with the various requirements of the USB 3.0 specification—such as signal eye diagrams, electromagnetic radiation, and electrostatic discharge (ESD) performance.
Attachment USB cable reference design drawing
