Voltage grades — what each one controls
The 1.5SMCJ78CA-AQ: The 78 V reverse standoff (typ) is the maximum working voltage the diode sees in normal operation — the protected rail sits below this, and the TVS stays off until a transient lifts it above the breakdown threshold. Once the transient exceeds 86.7 V minimum breakdown, the device avalanches and clamps the voltage to 126 V maximum at 11.9 A peak pulse (10/1000 µs waveform), shunting the surge current away from downstream circuitry — the 126 V ceiling is what the downstream IC or MOSFET gate sees.
Automotive temperature grade
A module mounted near the alternator or DC-DC converter that runs at 125°C ambient still has thermal headroom before the junction ceiling is hit. The automotive application flag means Diotec qualifies this part for the typical automotive screening and traceability stack — confirm lot traceability and any AEC-Q101 alignment requirements with your Diotec sales contact before committing to a new design.
SMC/DO-214AB footprint
Surface-mount SMC (DO-214AB) package with a thermal pad under the body — the cathode bar is the larger pad; PCB layout should keep the pad solder-wetted to the landing pattern to maintain the rated thermal resistance to the board. Strip packaging is the standard reel-free format for prototype reels and manual-assembly runs; confirm the full reel quantity requirement for production quant.