Figure 13. Reference design of USB interface circuit
5.5.2. USB Routing Rules
5.5.2.1. USB 2.0 Routing Rules
Since the module supports USB 2.0 High-Speed, TVS Junction capacitance on the
USB_D+/D– differential signal line must be less than 1 pF, and a 0.5 pF TVS is
recommended.
USB_D– and USB_D+ are high speed differential signal lines with the maximum
transmission rate of 480 Mbit/s. The following rules must be strictly followed in PCB
layout:
•
USB_D– and USB_D+ signal lines should have the differential impedance of
90
Ω
±10
Ω
.
•
USB_D– and USB_D+ signal line difference must be less than 2mm in length and
parallel, avoiding the right-angle routing.
•
USB_D– and USB_D+ signal lines should be routed on the layer that is closest to the
ground layer, and protected with GND all around.
5. Functional Interface
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