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⚫
Place the (U)SIM card connector as close to the module as possible. Keep the trace length as less
than 200 mm as possible.
⚫
Keep (U)SIM card signals away from RF and power supply traces.
⚫
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with surrounded ground.
⚫
For better ESD protection, it is recommended to add a TVS array with parasitic capacitance not
exceeding 15 pF.
⚫
The 0 Ω resistors should be added in series between the module and the (U)SIM card connector to
facilitate debugging. Additionally, add 33 pF capacitors in parallel among USIM_DATA, USIM_CLK
and USIM_RST signal traces to filter out RF interference. Note that the (U)SIM peripheral circuit
should be close to the (U)SIM card connector.
⚫
The pull-up resistor on USIM_DATA trace can improve anti-jamming capability when long layout trace
and sensitive occasion are applied, and it must be placed close to the (U)SIM card connector.
4.2. USB Interface
RG255C-GL 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
(480 Mbps) mode and full-speed (12 Mbps) mode.
The USB interface is used for AT command communication, data transmission, GNSS NMEA output,
software debugging and firmware upgrade.
The following table shows the pin definition of USB interface.
Table 9: Pin Definition of USB Interface
Pin Name
Pin No.
USB_DM
36
USB_DP
38
RG255C-GL_Mini_PCIe_Hardware_Design
I/O
Description
AIO
USB 2.0 differential data (-)
AIO
USB 2.0 differential data (+)
5G Module Series
Comment
Requires differential impedance of 90 Ω.
Test points must be reserved.
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