What the 28V standoff and 50V clamping ceiling mean
The 1.5SMCJ28C is a unidirectional TVS Zener in DO-214AB (SMC) — a single-polarity device that clamps the protected line to 50 V when a transient exceeds the 31.1 V breakdown threshold. The 28 V reverse standoff rating is the working voltage the line sits at during normal operation; the clamping ceiling at 50 V is what the downstream circuitry sees during the surge event. For a 24 V rail, 28 V standoff gives roughly 4 V headroom — sufficient for line-length inductive kickback without premature conduction. At 50 V clamping, 30 A × 50 V = 1500 W, so the part is specced consistently across the datasheet.
Thermal and board integration
For steady-state reverse bias at 28 V the dissipation is negligible; the 150 °C TJ ceiling matters only during the pulse. SMC (DO-214AB) is the mid-size surface-mount package — larger pad lands than SOD-123, adequate copper pour under the cathode tab for transient heat spreading. The surface-mount form factor suits reflow assembly on multi-layer boards.
Sourcing posture — Diotec, active production
Sourced through independent distribution; availability and lead time confirmed at quote.