Usb Interface - Quectel EG91 Series Hardware Design

 Assure the ground trace between the module and the (U)SIMcard connector short and wide. Keep
the trace width of ground and USIM_VDD no less than 0.5mm to maintain the same electric potential.
Make sure the bypass capacitor between USIM_VDD and USIM_GND less than 1uF, and place it as
close to (U)SIM card connector as possible.If the ground is complete on customers' PCB,
USIM_GND can be connected to PCB ground directly.
 To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away fromeach other and
shield them with surrounded ground.
In order to offer good ESD protection, it is recommended to add a TVSdiode array whose parasitic

capacitance should not be more than15pF. The 0Ωresistors should be added in series between the
module and the (U)SIMcard to facilitate debugging. The 33pFcapacitors are used for filtering
interference of EGSM900.Please note that the (U)SIMperipheral circuit should be close to the
(U)SIMcard connector.
 The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout trace
and sensitive occasion areapplied, and should be placed close to the (U)SIMcard connector.

NOTE
"*" means under development.
EG91 contains one integrated Universal Serial Bus (USB) interfacewhich 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 communication, data transmission, GNSS NMEA sentences output,software
debugging, firmware upgrade and voice over USB*. The following table shows the pin definition of USB
interface.
Table 10: Pin Definition of USB Interface
Pin Name Pin No.
USB_DP 9
USB_DM 10
USB_VBUS 8
GND 3
For more details about USB 2.0 specifications, please visit http://www.usb.org/home.
EG91_Hardware_Design

3.10. USB Interface

I/O Description
IO USB differential data bus (+)
IO USB differential data bus (-)
PI USB connection detection
Ground
44 / 93
LTE Module Series
EG91 Hardware Design
Comment
Require differential
impedance of 90Ω.
Require differential
impedance of 90Ω.
Typical:5.0V