Quectel SC20 Series Hardware Design page 48

SC20 series supports (U)SIM card hot-plug via the USIM_DETECT pin. A reference circuit for (U)SIM
interface with an 8-pin (U)SIM card connector is shown below.
Figure 17: Reference Circuit for (U)SIM Interface with an 8-pin (U)SIM Card Connector
If there is no need to use USIM_DETECT for (U)SIM card hot-plug, keep it open. The following is a
reference circuit for (U)SIM interface with a 6-pin (U)SIM card connector.
Figure 18: Reference Circuit for (U)SIM Interface with a 6-pin (U)SIM Card Connector
In order to ensure good performance and avoid damage to (U)SIM cards, follow the criteria below in
(U)SIM circuit design:
Keep placement of (U)SIM card connector as close to the module as possible. Keep the trace length

of (U)SIM card signals as less than 200 mm as possible.
Keep (U)SIM card signals away from RF and VBAT traces.

A filter capacitor shall be reserved for USIM_VDD, and its maximum capacitance should not exceed

1 μF. The capacitor should be placed close to the (U)SIM card connector.
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