5.6 V zener — regulation and clamping
The 1N4734AUR: With a nominal zener voltage of 5.6 V and ±5% tolerance, this diode provides a stable reference for voltage regulation, overvoltage clamping, or shunt-regulator circuits. The 5.6 V point sits near the zero-temperature-coefficient knee for a zener — a common choice where temperature drift matters in the reference rail.
DO-213AB MELF — high-reliability surface-mount package
The DO-213AB MELF (Metal Electrode Leadless Face) package is a glass-passivated, cylindrical body with metallized end caps. The MELF footprint is non-standard versus SOD-123 or SOT-23 — the cylindrical body requires a specific pad layout to avoid tombstoning during reflow. Confirm the board land pattern against the Microchip application note for DO-213AB before committing the PCB.
Parametric notes for the BOM
Maximum impedance (Zzt) is 5 Ohms at the test current — this sets the dynamic resistance and influences how tightly the zener regulates under varying load current. A lower Zzt means better regulation, and 5 Ohms is typical for a 5.6 V, 1 W device in this package class. Reverse leakage is specified at 10 µA maximum at 2 V reverse bias — well below the zener threshold, confirming the diode blocks cleanly until it reaches the breakdown region. Forward voltage drop is 1.2 V maximum at 200 mA forward current — useful if the diode is occasionally forward-biased in a clamping or protection application.