7.5 V Zener in a hermetic SQ-MELF package
The 1N6321US/TR is a 7.5 V Zener diode rated for 500 mW continuous power dissipation, housed in a hermetic SQ-MELF (B) package. The ±5% tolerance on the nominal Zener voltage gives a regulation window of 7.125 V to 7.875 V, which matters for precision clamping or reference applications where the rail must stay within a tight band. The SQ-MELF case is a surface-mount ceramic package with metallized end caps, designed for high-reliability soldering onto a PCB or hybrid substrate. The -65°C to 175°C junction temperature range suits it for avionics, downhole, or satellite power bus conditioning where the ambient swings wide.
Zener impedance and leakage — what limits the regulation
Maximum dynamic impedance (Zzt) is 4 Ohms at the Zener test current. A lower Zzt means the output voltage shifts less under varying load current — at 10 mA load swing the output moves under 40 mV, keeping the rail stable for sensitive analog supplies. Reverse leakage is specified at 2 µA maximum at 5 V reverse bias. For a 7.5 V rail that is 33% below the breakdown knee, the leakage stays negligible — a 5 V bias on the Zener draws less than 2 µA, so it will not load down a high-impedance sensing node. Forward voltage is 1.4 V maximum at 1 A forward current. This means the die can also serve as a high-current rectifier in the forward direction — the 500 mW power limit still applies, so the forward current must stay within the thermal budget.