3.3 V Zener with 5 W dissipation
The 1N6632US is a 3.3 V Zener diode rated for 5 W continuous power dissipation in a surface-mount SQ-MELF B package. The ±5% tolerance on the nominal Zener voltage means the actual breakdown sits between 3.135 V and 3.465 V at the test current — tight enough for a basic shunt regulator or voltage reference, but not for precision analog rails where a 1% or 0.5% part would be specified. The 5 W rating is the maximum power the diode can dissipate when the case temperature is held at 25°C or below. In practice, derate this figure for ambient temperatures above 25°C — the thermal resistance of the SQ-MELF package to the board determines how much current the diode can actually shunt. At 3.3 V, 5 W corresponds to roughly 1.5 A of Zener current, but the board layout and copper area under the package will limit that in a real assembly.
Temperature range and reverse leakage
Operating from -65°C to 175°C, the 1N6632US covers military and industrial temperature extremes without derating the voltage specification. The wide range suits avionics, downhole instrumentation, and engine-bay electronics where the ambient can swing beyond standard commercial limits. Reverse leakage is specified at 300 µA maximum when 1 V is applied across the junction — that is well below the Zener voltage, so it represents the leakage before breakdown. At elevated temperatures leakage rises exponentially; at 175°C the actual leakage may approach the milliampere range, which matters for battery-powered or high-impedance bias circuits where standby current must stay low.
Active production and sourcing
The SQ-MELF B package (D-5B supplier device code) is a hermetic ceramic surface-mount package with a metallized termination band. It is designed for high-reliability soldering processes and offers good thermal cycling performance compared to plastic packages.