Usb Interface - Quectel LTE Standard Module Series Hardware Design


Make sure the bypass capacitor between USIM_VDD and USIM_GND is less than 1uF, and be
placed 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 from each other and
shield them with surrounded ground.

In order to offer good ESD protection, it is recommended to add a TVS diode with parasitic
capacitance not exceeding 15pF.

The 0Ω resistors should be added in series between the module and the (U)SIM card connector so
as to facilitate debugging. The 33pF capacitors are used for filtering interference of EGSM900.
Please note that the (U)SIM peripheral circuit should be close to the (U)SIM card 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 (U)SIM card connector.

3.5. USB Interface

EG21-G Mini PCIe provides one integrated Universal Serial Bus (USB) interface which complies with
USB 2.0 specification. It can only be used as a slave device. Meanwhile, it supports high speed (480Mbps)
mode and full speed (12Mbps) mode. The USB interface is used for AT command communication, data
transmission, GNSS NMEA output, software debugging, firmware upgrade and voice over USB.
The following table shows the pin definition of USB interface.
Table 8: Pin Definition of USB Interface
Pin Name Pin No.
USB_DM 36
USB_DP 38
Module
EG21-G_Mini_PCIe_Hardware_Design
I/O Description
IO USB differential data (-)
IO USB differential data (+)
Minimize these stubs
USB_DM
USB_DP
ESD Array Close to Module
GND
Figure 6: Reference Circuit of USB Interface
EG21-G Mini PCIe Hardware Design
Comment
Require differential impedance of 90Ω
Require differential impedance of 90Ω
Test Points
R3 NM_0R
NM_0R
R4
L1
LTE Standard Module Series
MCU
USB_DM
USB_DP
GND
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