Quectel EC200U Series Hardware Design page 46

interface only supports USB slave mode and it can be used for AT command communication, data
transmission, software debugging and firmware upgrade.
Table 14: Pin Description of USB Interface
Pin Name Pin No.
USB_DP 69
USB_DM 70
USB_VBUS 71
GND 72
For more details about the USB 2.0 specifications, please visit http://www.usb.org/home.
Reserve test points for debugging and firmware upgrade in your design. The following figure shows a
reference circuit of USB interface.
Module
USB_VBUS
USB_DM
USB_DP
GND
A common mode choke L1 is recommended to be added in series between the module and your MCU in
order to suppress EMI spurious transmission. Meanwhile, the 0 Ω resistors (R3 and R4) should be added
in series between the module and the test points so as to facilitate debugging, and the resistors are not
mounted by default. In order to ensure the integrity of USB data line signal, L1, R3 and R4 components
must be placed close to the module, and also these resistors should be placed close to each other. The
EC200U_Series_Hardware_Design
I/O Description
AIO USB differential data bus (+)
AIO USB differential data bus (-)
AI USB connection detect
Ground
Minimize these stubs
R3
R4
VDD
L1
Close to Module
Figure 19: Reference Circuit of USB Application
Test Points
NM_0R
NM_0R
ESD Array
LTE Standard Module Series
Comment
Require differential
impedance of 90 Ω
Require differential
impedance of 90 Ω
Typical 5.0 V,
Minimum 3.5 V
MCU
USB_DM
USB_DP
GND
41 / 94