13 V regulation in a hermetic MELF
The 1N6327DUS/TR is a 13 V zener diode from Microchip Technology, rated for 500 mW continuous power dissipation in a hermetic SQ-MELF B surface-mount package. The ±1% tolerance on the nominal zener voltage means the regulation window is tighter than a standard 5% zener — the output rail stays within 130 mV of 13 V across the operating current range, which matters for precision bias supplies or ADC reference circuits.
The 8 Ohm maximum zener impedance (Zzt) at the test current sets the dynamic regulation: a 10 mA change in zener current shifts the voltage by 80 mV worst-case. For a load that draws 5–15 mA, the output stays within 80 mV of 13 V without an external pass element. Reverse leakage is specified at 50 nA maximum when the applied voltage is 9.9 V — 3.1 V below the zener knee. In a battery-powered circuit where the zener sits across the rail as a clamp, this leakage adds less than 0.5 µW of standby loss at room temperature. The forward voltage is 1.4 V maximum at 1 A forward current — the diode conducts in the forward quadrant with a drop comparable to a standard signal diode, useful if the part also serves as reverse-polarity protection in a low-current path.
Package and temperature range
The SQ-MELF B package is a hermetic, ceramic-bodied surface-mount form factor with metallized end caps — it seals the die against moisture and outgassing, making it suitable for high-reliability, aerospace, or downhole applications where a plastic SOT-23 or SOD-123 would not survive. The 500 mW power rating must be derated above 25°C ambient per the thermal resistance of the board footprint.