What the voltage ratings mean for your circuit
The 1.5SMCJ24A: Reverse standoff voltage is 24 V typ — the TVS sits idle below this and activates only when the line exceeds 26.7 V minimum breakdown. Once conducting, it clamps at a maximum 38.9 V, which sets the downstream IC withstand requirement. Peak pulse current is 38.6 A at the 10/1000 µs spec wave — the 1500 W rating is derived from 38.6 A × 38.9 V clamping. If the surge is shorter or the clamping voltage lower, the device can survive more current; longer-duration events derate the available current accordingly. Junction temperature range is -50°C to 150°C, which covers the automotive and industrial envelope — the upper limit is the semiconductor junction, not the ambient, so the board-level thermal path determines how much margin remains at operating ambient.
Board integration — SMC footprint
Surface-mount SMC/DO-214AB package is the industry-standard footprint for 1.5–3 kW TVS diodes — pin-compatible across most suppliers. The anodes and cathode orientation matters for unidirectional polarity — confirm the schematic symbol before layout.