15 V regulation, 1 W dissipation — the rail clamp for a 12 V bus
Microchip Technology's 1N4744AP/TR8 is a 15 V Zener diode in the standard DO-204AL (DO-41) axial-lead package, rated for 1 W continuous power dissipation. The ±5% tolerance on the nominal 15 V breakdown means the actual clamping voltage falls between 14.25 V and 15.75 V at the specified test current — tight enough to protect a 12 V rail from transients without eating into the operating margin.
Active production — sourced per RFQ
This part carries an active lifecycle status from Microchip Technology.
Dynamic impedance and leakage — the real-world guard bands
Maximum Zener impedance (Zzt) is 14 Ohms at the knee — this is the incremental resistance the regulator sees; a higher load current through the diode raises the voltage drop across this impedance, shifting the clamp point slightly above 15 V. Reverse leakage is specified at 5 µA maximum at 11.4 V, so the diode draws negligible current below the breakdown region, preserving battery life in a standby shunt regulator.
Temperature range and forward drop
Forward voltage is 1.2 V maximum at 200 mA — relevant if the diode sees brief forward conduction in an AC or reverse-polarity condition.