Robust and reliable bus node design often requires the use of external transient protection devices to protect against surge transients that may occur in industrial environments. THVD4431 has integrated IEC ESD and EFT protection. So if the application does not need IEC Surge protection, external transient protection may not be needed. Since these transients have a wide frequency bandwidth (from approximately 3 MHz to 300 MHz), high-frequency layout techniques should be applied during PCB design.

1. Place the external protection circuitry close to the bus connector to prevent noise transients from propagating across the board.
2. Use V_CC and ground planes to provide low inductance. Note that high-frequency currents tend to follow the path of least impedance and not the path of least resistance.
3. Design the protection components into the direction of the signal path. Do not force the transient currents to divert from the signal path to reach the protection device.
4. Apply decoupling capacitors and charge pump capacitors as close as possible to the respective device pins such as V_CC, V_IO, V+, V-, C1+ to C1-, C2+ to C2- pins of transceiver.
5. Use at least two vias for V_CC and ground connections of decoupling capacitors and protection devices to minimize effective via inductance.
6. Optionally, use 1-kΩ to 10-kΩ pull-up and pull-down resistors for control lines to limit noise currents in these lines during transient events.