The 1.5SMC39A TR13 PBFREE: The 1500 W peak pulse power at 10/1000 µs is the industry-standard rating for this package size — it tells you the device can absorb a 28 A, 53.9 V transient for that duration. This part is a natural fit for 24 VDC rails (nominal 24 V + 20% tolerance = 28.8 V, well under 33.3 V) and for 28 V aircraft or military buses. The 37.1 V minimum breakdown gives a 3.8 V guard band above the standoff before avalanche starts. Unidirectional (single-channel) means the cathode band goes toward the rail being protected, anode to ground — orientation matters. For AC lines or bidirectional protection, you would need two devices back-to-back or a bidirectional part. No power line protection rating means it is intended for signal or low-power DC rails, not mains AC.
DO-214AB (SMC) is a standard footprint shared with many 1500 W TVS diodes from Littelfuse, Vishay, and STMicroelectronics — the pad layout is JEDEC-compatible, so this part drops into an existing SMC land pattern without a board spin. The body is about 7.1 mm × 6.2 mm, which fits a standard 12 mm tape pocket for automated pick-and-place. For a rework tech, the cathode band is clearly marked on the body; no special orientation beyond that.