3.3.6.1 PLC Rejection Filter

When the PLC coupling circuit is in parallel with the power supply circuit, the input impedance of the final equipment could be affected. If the requirements about total input impedance are not satisfied, an appropriate input filter is needed at the power supply input to increase the input impedance.

Apart from the input filter, it is also recommended to add a PLC rejection filter to avoid the absorption of the PLC signals by the power supply circuit. This filter also increases the input impedance, so it helps to achieve the requisites about input impedance.

Notice: The PL360G55CF-EK board has PLC coupling and power supply circuits separated, so the PLC rejection filter is not included. A PLC rejection filter is needed in case of low input impedance after connecting in the same point the PLC Coupling connector J1 and the power source of the board.

An example of PLC rejection filter is composed of two inductance in-series (L = 560 μH) and a capacitor in-parallel (C = 100 nF) at the power supply input as shown in the following picture.

Figure 3-14. PLC Rejection Filter Example