91 V rail clamp — sizing the zener for the application
The SML4763AHE3_A/I is a 91 V nominal zener diode from Vishay's Automotive AEC-Q101 series, rated for 1 W continuous power dissipation in a DO-214AC (SMA) surface-mount package. The ±5% tolerance on the zener voltage means the regulation point sits between 86.45 V and 95.55 V — a spread that matters when the downstream circuit has a tight overvoltage trip threshold.
Temperature range and derating
Operating from -65°C to 150°C, this diode covers the full automotive under-hood and military temperature envelope. At 150°C junction temperature the 1 W power rating must be derated per the standard SMA thermal resistance curve — the copper pad area under the cathode tab directly sets the junction-to-ambient thermal path.
The AEC-Q101 qualification means this part has passed the automotive-grade stress tests: temperature cycling, high-temperature reverse bias, and humidity. For a BOM that needs a 91 V clamp in an ECU, ABS module, or battery-management system, this qualification removes the need for a separate qualification run on a commercial-grade zener.