3.6 V rail clamp or reference in a hermetic surface-mount package
The 1N6633US is a 3.6 V Zener diode rated for 5 W continuous dissipation in the E-MELF (D-5B) hermetic surface-mount package. The 3.6 V nominal breakdown at ±5% tolerance sets the regulation window for a low-voltage rail clamp or shunt reference, while the 5 W power rating means the junction-to-solder thermal path through the E-MELF end-cap terminations must carry the full dissipation — the copper pad area on the board sets the real-world derating.
Reverse leakage and forward drop — the bias-circuit checkpoints
Reverse leakage is 250 µA maximum at 1 V reverse — well below the Zener knee, so a bias resistor string that holds the diode at 1 V sees negligible current draw. Forward voltage is 1.5 V maximum at 1 A, which matters if the diode sees surge current in the forward direction during a reverse-polarity event. Maximum Zener impedance (Zzt) is 500 Ohms at the test current; this sets the dynamic resistance the downstream circuit sees as the Zener regulates. A 500-Ohm impedance at 3.6 V means the output shifts about 0.5 V per mA of load change — adequate for a clamp or a low-accuracy reference, but not for a precision bias rail.