Zener regulation at 4.3 V, 2 W DO-214AC
The SMAJ4731CE3/TR13 is a 4.3 V Zener diode from Microchip Technology, rated for 2 W continuous power dissipation in the DO-214AC (SMA) surface-mount package. The ±2% tolerance on the nominal voltage means the actual breakdown sits between 4.214 V and 4.386 V at the test current — tight enough for a reference rail in a low-precision regulator or a clamp threshold where the guard band matters more than the absolute value. Maximum impedance (Zzt) is 9 Ohms at the zener test current, so the regulation slope is shallow — a 10 mA change in bias current shifts the output voltage by about 90 mV. Reverse leakage is specified at 10 µA maximum with 1 V reverse bias, which is the leakage floor before the junction enters breakdown.
DO-214AC footprint and assembly
The DO-214AC (SMA) package is a standard JEDEC outline with a 2.6 mm body width and gull-wing leads. The tape-and-reel format (TR suffix) feeds into a pick-and-place machine without a reel change — the carrier tape pitch is 4 mm per JEDEC 8 mm tape width. The cathode band on the body matches the polarity mark on the PCB silkscreen; a reversed diode blocks instead of regulating. The junction-to-ambient thermal resistance for the SMA body on a standard FR-4 pad is roughly 90°C/W — at 2 W dissipation the junction sits 180°C above ambient, so the 150°C limit derates the part to about 1.4 W at 85°C ambient.
Microchip lists this part as Active. The base product number SMAJ473 covers the family; the CE3 suffix indicates the ±2% tolerance grade and the /TR13 denotes the tape-and-reel packaging. Sourced through independent distribution channels.