Quectel QuecOpen BG952A-GL Hardware Design page 38

If (U)SIM card detection function is not needed, keep USIM_DET unconnected. A reference circuit for
(U)SIM interface with a 6-pin (U)SIM card connector is illustrated in the following figure.
Figure 15: Reference Circuit of (U)SIM Interface with a 6-Pin (U)SIM Card Connector
To enhance the reliability and availability of the (U)SIM card in applications, follow the criteria below in
(U)SIM circuit design:
Keep the placement of (U)SIM card connector as close to the module as possible. Keep the trace

length less than 200 mm.
Keep (U)SIM card signals away from RF and VBAT traces.
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Assure the ground trace between the module and the (U)SIM card connector short and wide. Keep
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the trace width of ground and USIM_VDD no less than 0.5 mm to maintain the same electric potential.
Make sure the bypass capacitor between USIM_VDD and USIM_GND is less than 1 μF, and place it
as close to (U)SIM card connector as possible. If the system ground plane is complete, USIM_GND
can be connected to the system ground directly.
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
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shield them with surrounded ground. USIM_RST should also be surrounded with ground.
To offer good ESD protection, it is recommended to add a TVS diode array with parasitic capacitance

not exceeding 15 pF. to facilitate debugging, it is recommended to reserve series resistors for the
(U)SIM signals of the module. The 33 pF capacitors are used for filtering interference of EGSM900.
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.
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LPWA Module Series
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