What this 1500W bidirectional TVS covers on the rail
The 1.5SMC150CAHE3/9AT: It clamps transients on a 128 V nominal rail — the reverse standoff voltage — and breaks down at 143 V minimum, with a maximum clamping voltage of 207 V at the 7.2 A peak pulse current (10/1000 µs waveform). That 1500 W rating means it can absorb a single 10/1000 µs surge up to that power level without failing short — the scorch mark tells you if the energy exceeded the part's capability. For a 24 V or 48 V automotive bus, this device sits on the higher-voltage side, typically used on the secondary side of an isolated DC-DC or on a 120 V nominal intermediate bus.
Package and board-fit: DO-214AB (SMC)
Housed in the DO-214AB (SMC) package, the same footprint as the SMCJ suffix. Surface-mount, with the cathode band marking the orientation for unidirectional parts — but this is a bidirectional channel, so polarity does not matter. The package sits low-profile on the board, and the copper pad area under the tab sets the thermal resistance for repetitive pulse handling. Operating junction temperature range is -65°C to +150°C, covering the full automotive under-hood and cabin ambient.