How should surge protection for concentrators be designed in a tiered manner?

Surge protection for concentrators must be designed in stages according to the IEC 61000-4-5 standard to cope with lightning strikes and switching transients. A typical three-stage protection system works as follows:

Stage 1 (coarse protection) is located at the power input, using a gas discharge tube (GDT) such as 2R600L-8×6 or a varistor (MOV) such as 14D511K.

Stage 2 (intermediate protection) is located at the board-level power input, using a varistor (such as 7D390K) or a TVS diode (such as SMCJ33CA).

Stage 3 (fine protection) is a TVS diode (such as SMBJ5.0CA) near the chip's power pin.

Each stage needs to be decoupled through inductors (such as common-mode inductors CMZ1211-501T) or resistors to achieve energy coordination. Communication ports also require staged protection, such as using a GDT+TVS combination. The current carrying capacity and response time of each stage of the device must be calculated during the design phase. Through this staged design, the concentrator can withstand surges of 4kV common-mode and 2kV differential-mode.