SLUSB72D March 2013 – April 2021 UCD3138064
UART is used for communicating between the primary side and secondary side with isolation boundary. Normally, the communication wires are long. These wires can easily be interfered by EMI and pick up noise of switching power supplies. First, the wires must be routed without directly exposing the traces to the switching noise source, and then a termination is needed at the end of the trace, as shown in Figure 12-7. For example, R = 50 Ω, C = 47 pF if they don’t significantly slow down the slew rate of the signals. When the pins are not used, tie them to the single ground plane SGND.