Quectel SC200L-EM Hardware Design page 32

In order to ensure USB performance, please comply with the following principles while designing a USB
interface.
 It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90Ω.
 Keep the ESD protection devices as close as possible to the USB connector. Pay attention to the
influence of junction capacitance of ESD protection devices on USB data lines. Typically, the
capacitance value should be less than 2pF.
 Do not route signal traces under crystals, oscillators, magnetic devices, and RF signal traces. It is
important to route the USB differential traces in inner-layer with ground shielding on not only the
upper and lower layers but also the right and left sides.
 Make sure the trace length difference of USB 2.0 is not exceeding 0.7 mm.
Table 9: USB Trace Length Inside the Module
PIN Signal
13 USB_DM
14 USB_DP
SC200L_Hardware_Design
Figure 11: USB OTG Interface Reference Design
Length (mm)
17.67
17.50
SC200L Hardware Design
Length Difference (DP-DM)
0.17
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