J301 SoM_IoT_1V2

Owned by Steffen Schröder
Last updated: Mar 04, 2022
3 min read

Figure 5 display the highlighted 9 pin connector J301 on bottom side of SoM_IoT_1V2 printed circuit board. With connector J301 are two 10BASE-T, 100BASE-TX/FX ethernet ports realized. The SoM-iRJ45 module includes the R-IN32M3-EC Ethernet Switch with additional TVS array connection for ESD and transient protection. Furthermore, the magnetic components for galvanic decoupling and signal integrity are offered too.

 

Figure 5: SoM_IoT_1V2 J301

 

Pin 19 (RX0_N) connect the differential receiver_N signal of ethernet port 0 and transfer this signal to target device. On this page below are detailed information of decoupling components and connection for J301 pins given.

 

Pin 20 (RX0_P) connect the differential receiver_P signal of ethernet port 0 and transfer this signal to target device.

 

Pin 21 (TX0_N) connect the differential transceiver_N signal of ethernet port 0 and transfer this signal to target device.

 

Pin 22 (TX0_P) connect the differential transceiver_P signal of ethernet port 0 and transfer this signal to target device.

 

Pin 23 (SHIELD) connect the external Ethernet-Shield for both ethernet ports.

 

Pin 24 (RX1_N) connect the differential receiver_N signal of ethernet port 1 and transfer this signal to target device.

 

Pin 25 (RX1_P) connect the differential receiver_P signal of ethernet port 1 and transfer this signal to target device.

 

Pin 26 (TX1_N) connect the differential transceiver_N signal of ethernet port 1 and transfer this signal to target device.

 

Pin 27 (TX1_P) connect the differential transceiver_P signal of ethernet port 1 and transfer this signal to target device.

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).

Schematic 2: Magnetic topology integrated HX1188

Following Schematic 3 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.

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.

Note: It is recommended the open pins of the external Ethernet connectors on carrier board, for RJ45 Jacks the pin 4/5 and 7/8, to decouple with 75Ω resistors and 1MΩ resistor to shield potential.

Ethernet Shield Connection

The Ethernet shielding connection for the external cabling shield has to be connected at J301 pin 23. Which is pictured in Schematic 3. This potential (J301_Pin23) 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 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!