How do self-resetting fuses and TVS work together in a data center switch?

The data center switch's self-resetting fuse and TVS form a collaborative overcurrent and overvoltage protection architecture. A typical connection is as follows: a TVS such as the Etymotic SMBJ15A (VRWM=15V clamping voltage 24.4V) is connected in parallel at the power input to absorb surge spikes; a PTC such as the SMD2920-150-16V is connected in series before the TVS to limit current. When a surge occurs, the TVS responds with a <1ns conduction clamp, and the PTC's thermal inertia prevents it from acting quickly enough, thus absorbing the surge energy. If the fault persists with overcurrent, the PTC's Joule thermal triggering high-resistance state limits the current to <200mA, protecting the TVS from thermal runaway. This collaborative architecture can withstand the dual stress of IEC61000-4-5 4kV surge and overcurrent. Actual measurements show that the TVS junction temperature is 28℃ lower than with separate protection, extending its lifespan by 3 times.