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What are the differential pairs of USB signals?
The USB differential pairs are signals labeled as D+ and D-. If both signal traces have mismatched lengths, the edges of the signal will arrive at the receiver at different time. This is more pronounced in higher speed protocols. At a frequency like 480 Mbps or 10 Gbps, USB traces can be a source of EMI interfering other signals on the PCB.
What are the impedance requirements for differential pair routing?
You’ve heard that differential pair routing requires both traces to match in length and parallel to each other. Follow the advice closely when you’re routing USB signal pairs. The USB standards require the signal traces impedance to be matched at 90 ohms, which is those of the USB cable.
What kind of signals does a USB Type C plug deliver?
USB Type-C Plug Signals (Source: Cypress Semiconductor) The USB Type-C Receptacle functionally delivers both USB 3.1 (TX and RX pairs) and USB 2.0 (D+ and D−) data buses, USB power (VBUS), ground (GND), Configuration Channel signals (CC1 and CC2), and two Sideband Use (SBU) signal pins.
How are USB 2.0 and V bus signals maintained?
GND, USB 2.0 and V BUS signals maintain connection. USB 2.0 signals are repeated in the top and bottom rows of the Type-C receptacle to maintain connectivity in either orientation. V CONN or CC pin on the plug may be connected to either of the configuration channel pins – CC1 or CC2 of the receptacle – depending upon the orientation.
Are there any issues with USB bus routing?
Risk of issues with USB routing increases with bus speed. As a PCB designer, you shouldn’t be nonchalant in your design approach. With that said, some USB designs are susceptible to issues if you made a mistake. If you’re designing a USB1.1 or USB2.0 full-speed device, the maximum rate you need to contend with is 12 Mbps, and seldom causes issues.
Why are USB traces interfering with other signals?
At a frequency like 480 Mbps or 10 Gbps, USB traces can be a source of EMI interfering other signals on the PCB. Of course, the effect can be mitigated by employing best practices that deal with high-speed signals. It doesn’t matter if you’re working on a USB1.1 or the speedy USB3.1.