400 W bidirectional TVS in DO-214AC — what it protects and where
The STMicroelectronics SMAJ130CA-TR is a bidirectional TRANSIL™ transient voltage suppressor diode in the SMAJ series. It is designed to clamp voltage spikes on general-purpose power and signal lines, with a peak pulse power rating of 400 W (10/1000 µs waveform). The device offers a reverse standoff voltage of 130 V and a maximum clamping voltage of 265 V at the peak pulse current of 9 A (8/20 µs).
For a 130 V nominal rail, that's roughly twice the operating voltage — typical for a TVS in this class. The breakdown voltage range starts at 144 V minimum, so the device begins conducting before the voltage climbs much above the standoff level. This gives a reasonable protection window for 120 VAC or 130 VDC rails, though the designer should verify the downstream components' voltage rating against the clamp figure.
A single bidirectional channel means the SMAJ130CA-TR clamps equally in both directions. That simplifies board layout for AC signal lines, bipolar supplies, or data lines where the polarity isn't fixed. No need to back-to-back two unidirectional devices — one component handles it. The DO-214AC footprint is standard and pick-and-place friendly.