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. THVD4411 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 3MHz to 300MHz), high-frequency layout techniques
should be applied during PCB design.
- Place the external protection
circuitry close to the bus connector to prevent noise transients from
propagating across the board.
- Use VCC 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.
- 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.
- Apply decoupling capacitors
as close as possible to the VCC, VIO, V+, V- pins of
transceiver.
- Use at least two vias for
VCC and ground connections of decoupling capacitors and
protection devices to minimize effective via inductance.
- Optionally, use 1kΩ to 10kΩ
pull-up and pull-down resistors for control lines to limit noise currents in
these lines during transient events.