Quectel BC950N-N1 Hardware Design page 29

Table 11: Pin Definition of USB Interface
Pin Name Pin No.
USB_MODE 88
USB_3V3 85
USB_DP 87
USB_DM 86
The following is a reference design of USB interface:
Module
VUSB_3V3
USB_DM
USB_DP
GND
In the circuit design of USB interface, in order to ensure the performance of USB, the following principles
are suggested in the circuit design:

It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90Ω.

Do not route signal traces under power supply, RF signal traces and other sensitive signal traces. It is
important to route the USB differential traces in inner-layer with ground shielding on not only upper
and lower layers but also right and left sides.

Pay attention to the influence of junction capacitance of ESD protection components on USB data
lines. Typically, the capacitance value should be less than 3pF.

Keep the ESD protection components as close to the USB connector as possible.
BC950N-N1_Hardware_Design
I/O Description
DI Boot mode selection
PI USB power supply
IO USB differential data (+)
IO USB differential data (-)
3.3V
Figure 14: USB Interface Reference Design
LPWA Module Series
BC950N-N1 Hardware Design
Note
Pull this pin low to
implement USB
download function.
Suspended or pulled up
10KΩ resistor to 3.3V for
normal boot mode.
Vnorm=3.3V
Conform to USB 1.1
specifications.
Require 90Ω differential
impedance.
ESD Array
USB_DM
USB_DP
GND
PC
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