What the obsolete status means for your BOM
The 1.5SMC9.1: If the design is still in the field, the path forward is independent distribution: quantities are lot-specific, traceability is confirmed at quote, and a cross-reference search across the 1.5SMC family is the only way to surface a form-fit-function replacement. For a new design, this part is off the table; the 1.5SMC series itself may have newer TVS ratings in the same SMC package — the parametric family cross-reference is worth running before committing to any alternate.
The standoff-clamp spec set and what it means for protection
The 1.5SMC9.1 is a unidirectional TVS Zener in the DO-214AB (SMC) package — it protects a single polarity against transients by clamping. The reverse standoff voltage of 7.78 V is the working bias the TVS sees in normal operation; any spike that drives the line above that forward-conducts through the Zener action. That 14.07 V clamping ceiling is the number that protects whatever is behind it — the downstream IC sees 14.07 V as the stress limit, not the raw transient amplitude.
1500 W peak pulse and the junction temperature envelope
Rated for 1500 W peak pulse (1.5 kW) with a junction temperature ceiling of 150°C, the part survives the 10/1000 µs surge profile common in industrial and telecom supply rails. The SMC package thermal resistance to the board pads governs whether the part cycles reliably in your enclosure — at 113.4 A through the clamping voltage the instantaneous dissipation is over 1.5 kW, so the board copper under the cathode tab is the primary heatsink. Surface-mount TVS in this power class is typically reflow-soldered; the 1.5SMC series ships on tape and reel for automated placement.