Quectel UC20 Manual
Also see for UC20: Application noteUser guideUser guideUser guideHardware design
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UMTS/HSPA Module SeriesUC20 Hardware DesignUC20_Hardware_Design Confidential / Released 43 / 84Some AT commands are invalid when USIM card is not applied.UC20 supports USIM card hot-plugging via the USIM_PRESENCE pin. For details, refer to document [1]about the command AT+QSIMDET. If you do not need the USIM card detection function, keepUSIM_PRESENCE unconnected. The reference circuit for using a 6-pin USIM card connector isillustrated as the following figure.ModuleUSIM_VDDUSIM_GNDUSIM_RSTUSIM_CLKUSIM_DATA 22R22R22R100nF USIM ConnectorGNDESDA6V8AV633pF 33pF 33pFVCCRSTCLK IOVPPGNDGND15KUSIM_VDDFigure 23: Reference Circuit of the 6 Pin USIM CardIn order to enhance the reliability and availability of the USIM card in your application, please follow thefollowing criterion in the USIM circuit design: Keep layout of USIM card as close as possible to the module. Assure the length of the trace is lessthan 200mm. Keep USIM card signal away from RF and VBAT alignment. Assure the ground between module and USIM connector short and wide. Keep the width of groundand USIM_VDD no less than 0.5mm to maintain the same electric potential. The decouple capacitorof USIM_VDD should be less than 1uF and must be near to USIM connector. To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away with each other andshield them with surrounded ground. In order to offer good ESD protection, it is recommended to add TVS such as WILL(http://www.willsemi.com) ESDA6V8AV6. The 22Ω resistors should be added in series between themodule and the USIM card so as to suppress the EMI spurious transmission and enhance the ESDprotection. The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout traceand sensitive occasion is applied.NOTE |
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