Zener regulation at 4.7 V, 5 W in a hermetic MELF
The 1N6636US is a 4.7 V zener diode rated for 5 W continuous power dissipation in a SQ-MELF, E surface-mount package. The ±5% tolerance on the nominal voltage means the actual zener voltage at the test current falls between 4.465 V and 4.935 V — tight enough for most rail-clamp or reference applications that do not require a precision bandgap. Maximum zener impedance is 450 Ohms at the specified test current; this sets the dynamic resistance the load sees when the diode regulates. Reverse leakage is 20 µA at 1 V reverse bias, and forward voltage drop is 1.5 V max at 1 A — the diode can handle brief forward-current surges during reverse-polarity events without exceeding the junction rating.
Hermetic SQ-MELF package and temperature range
The SQ-MELF, E (D-5B supplier device package) is a hermetic, ceramic-bodied surface-mount package designed for high-reliability environments. The -65°C to +175°C operating temperature range covers military and aerospace thermal profiles — the hermetic seal prevents moisture ingress and parameter drift through temperature cycling. The package is supplied in Bulk format, which suits low-to-medium volume assembly or prototype builds where tape-and-reel handling is not required.