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FIBOCOM FM150-NA User Manual
Page 49 of 72
Since the module supports USB 2.0 High-Speed, it is required to use TVS diodes with equivalent
capacitance of 1pF or smaller ones on the USB_D-/D+ differential signal lines, it is recommended to use
0.5pF TVS diodes.
USB_D- and USB_D+ are high speed differential signal lines with the maximum transfer rate of480 Mbit/s,
so the following rules shall be followed carefully in the case of PCB layout:
USB_D- and USB_D+ signal lines should have the differential impedance of 90±10 ohms.
USB_D- and USB_D+ signal cables must be less than 2mm in length and parallel, the right angle
routing should be avoided.
USB_D- and USB_D+ signal lines should be routed on the layer that is adjacent to the ground layer,
and wrapped with GND vertically and horizontally.
3.4.2.3 USB3.0 Interface Application
The reference circuit is shown in Figure 3-16:
Figure 3-16 Reference Circuit for USB 3.1 Interface
USB 3.1 Gen2 signals are super speed differential signal lines with the maximum transfer rate of
10Gbps.So the following rules shall be followed carefully in the case of PCB layout:
USB_SS_TX-/US and USB_SS_RX-/ US are two pairs differential signal lines,
the differential impedance should be controlled as 90±10 ohms.
For TX differential line, the + and-traces must be parallel, equal length, and the length difference is
less than 0.7mm, avoiding right-angle traces.
For the RX differential line, the + and-traces must be parallel, equal length, and the length difference
is less than 0.7mm. Avoid right-angle traces.
TX and RX traces must be parallel, equal length, and the length difference is less than 10mm. Avoid
right-angle traces.The two pairs differential signal lines should be routed on the layer that is adjacent
to the ground layer, and wrapped with GND vertically and horizontally.
