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Exemplary magnetic topology
Following Schematic 2 pictured the used HX1188 magnetic circuit topology. Two of this component are on module PCB for both ethernet port integrated. The transmit part of HX1188 decouple both differential transmit signals (TxP/ TxN) for one ethernet port between MCU and RJ45 connector contacts. Equal to receive part of HX1188 for both differential receive signals (RxP/ RxN).Following Schematic 4 show the wiring concept of ethernet port 0 between MCU (R-IN32M3-EC) and Ethernet jack connection contacts. A consistent differential signal cabling is recommended. For deeper information about used HX1188 magnetic circuit topology see the J301 SoM_IoT_1V2 description.
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All components on left side of blue marked J301 connector are equipped on SoM_iRJ45 module. The schematically pictured RJ45 connector has to be placed on target device and is not part of SoM module.
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The Ethernet shielding connection for the external cabling shield has to be connected at J301 pin 2341. Which is pictured in Schematic 3. This potential (J301_Pin23Pin41) is recommended to connect with functional earth in the local operating environment. This ensures an interference deflection and protect the module method of operating.
Note: Do not connect J301 pin 23 41 with GND, otherwise all cable interspersed disturbances will have negative influence to module circuit. This SHIELD is internal decoupled with resistor/capacitor network to system GND!