Usb Interface - Quectel EC25-V User Manual

criteria below in the USIM circuit design:
Keep layout of USIM card as close as possible to the module. Assure the length of trace is less than

200mm.
Keep USIM card signal away from RF and VBAT alignment.

Assure the ground between the module and the USIM connector short and wide. Keep the width of

ground and USIM_VDD no less than 0.5mm to maintain the same electric potential.
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away with each other and

shield them with surrounded ground.
In order to offer good ESD protection, it is recommended to add TVS which parasitic capacitance

should not be more than 50pF. The 22ohm resistors should be added in series between the module
and the USIM card so as to suppress the EMI spurious transmission and enhance the ESD
protection. The 33pF capacitors are used for filtering interference of GSM900. Please note that the
USIM peripheral circuit should be close to the USIM connector.
The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout trace

and sensitive occasion are applied, and should be placed close to the USIM connector.

3.10. USB Interface

EC25 contains one integrated Universal Serial Bus (USB) transceiver which complies with the USB 2.0
specification and supports high-speed (480Mbps) and full-speed (12Mbps) modes. The USB interface is
used for AT command, data transmission, GNSS NMEA sentences output, software debug and firmware
upgrade. The following table shows the pin definition of USB interface.
Table 10: USB Pin Description
Pin Name Pin No.
USB_DP 69
USB_DM 70
USB_VBUS 71
GND 72
More details about the USB 2.0 specifications, please visit http://www.usb.org/home.
The USB interface is recommended to be reserved for firmware upgrade in your design. The following
figure shows the reference circuit of USB interface.
EC25-V_User_Manual
69
I/O Description
IO USB differential data bus (positive).
IO USB differential data bus (minus).
Used for detecting the USB
PI
connection.
Ground
Confidential / Released
LTE Module Series
EC25-V User Manual
Comment
Require differential
impedance of 90Ω.
Require differential
impedance of 90Ω.
Typical 5.0V
34 /