What this 1500W bidirectional TVS protects
The 1.5SMC10CA: Its 8.55V reverse standoff voltage means the protected rail can run at 8.55V DC without the diode conducting leakage current; the breakdown triggers at a minimum of 9.5V, so a 12V rail is too high for this part — it would sit in continuous avalanche. One bidirectional channel clamps both polarities in a single DO-214AB (SMCJ) surface-mount package, saving board space compared to back-to-back unidirectional pairs.
Temperature range and mounting
Surface-mount to DO-214AB (SMC) footprint; the 1500W rating assumes a standard copper-land pattern on the PCB — a smaller pad increases thermal resistance and reduces the effective pulse-handling capability.