4.7 V zener, 500 mW — the thermal budget trap
The 1N5230B-TAP is a 4.7 V zener diode in the DO-35 axial package, rated for 500 mW total power dissipation. The ±5% tolerance on the zener voltage means the actual clamp point can sit between 4.465 V and 4.935 V — tight enough for most shunt regulator and protection circuits, but worth checking if your load has a narrow supply window.
175°C junction — where it matters
The 175°C maximum operating temperature is 25°C above the standard automotive 150°C limit. That extra margin matters when the zener sits near a hot power device or in an under-hood ambient that hits 125°C. At 175°C junction, the 500 mW power rating still holds — but the reverse leakage at that temperature will be higher than the 5 µA at 2 V specified at 25°C, so budget for it in the bias network.
AEC-Q101 — not just a sticker
The AEC-Q101 qualification (Automotive, AEC-Q101 series) means this part has passed the automotive stress tests: high-temperature reverse bias, temperature cycling, and humidity. For a non-automotive design it is still a good reliability indicator — the same screening catches infant mortality that a commercial-grade zener might not.
DO-35 axial — the layout constant
Through-hole DO-35 (DO-204AH) body. The axial leads let you stand the diode upright or lay it flat against the board. The 19 ohm maximum zener impedance at the test current means the regulation slope is moderate — expect about 19 mV change in Vz per mA of current change near the test point.