Onsemi 1N5343BRLG 5W 13V Zener Diode: Datasheet, Application Circuit, and Replacement Guide

The Onsemi 1N5343BRLG is a robust 5W Zener diode designed for voltage regulation and overvoltage protection in a wide range of electronic circuits. As part of the popular 1N534x series, this component is known for its reliability and ability to handle higher power levels compared to standard Zener diodes. This article provides a detailed look at its specifications, a typical application circuit, and guidance for selecting a suitable replacement.

Datasheet Overview and Key Specifications

The 1N5343BRLG is a 5-watt, 13-volt Zener diode in an axial-leaded, DO-15 package. Its primary function is to maintain a constant voltage across its terminals, known as the Zener voltage (Vz), when it is reverse-biased and operating in its breakdown region.

Key parameters from its datasheet include:

Nominal Zener Voltage (Vz): 13 V at a test current (Izt) of 95 mA.

Power Dissipation (Ptot): 5 W at a case temperature (Tc) of 75°C.

Maximum Zener Impedance (Zzt): 3.5 Ω at Izt.

Voltage Tolerance: ±5% (B grade).

Operating Temperature Range: -65°C to +200°C.

A critical consideration for power Zeners is derating. The 5W power rating is only valid up to a case temperature of 75°C. As the ambient temperature increases beyond this point, the diode's ability to dissipate power decreases. Designers must consult the derating curve in the datasheet to ensure reliable operation at higher temperatures.

Application Circuit: Simple Voltage Regulator

A classic application for the 1N5343BRLG is a simple shunt voltage regulator. The circuit's purpose is to maintain a stable 13V output from a higher, unregulated input voltage (e.g., 18-20V), protecting a sensitive load from overvoltage.

How it works:

1. Current Limiting Resistor (Rs): This resistor is connected in series with the input voltage. It limits the total current flowing through the circuit, ensuring the Zener diode does not exceed its maximum power rating. Its value is calculated based on the input voltage, desired output voltage, and the load current.

2. Zener Diode (1N5343BRLG): The diode is connected in reverse bias between the output and ground. It acts as a shunt regulator, "clamping" the output voltage to 13V by conducting excess current to ground when the voltage tries to exceed its Vz.

3. Load (RL): The device or circuit that requires a stable 13V supply is connected in parallel with the Zener diode.

This circuit is effective for low-current applications or as a reference voltage. For higher current needs, the Zener can be used to bias the base of a power transistor to create a more efficient series pass regulator.

Replacement and Equivalent Guide

Finding a direct replacement for the 1N5343BRLG requires matching key electrical and physical characteristics.

Direct Equivalents: Look for parts with the same 5W power rating, 13V Zener voltage, and ±5% tolerance. Components from other manufacturers like Micro Commercial Components (MCC), Vishay, or Comchip may offer direct cross-references (e.g., MCC 1N5343B).

Key Parameters for Replacement:

1. Zener Voltage (Vz): Must be 13V.

2. Power Rating (Ptot): Must be 5W or higher. A higher wattage diode can be used for better reliability but may have a larger package.

3. Tolerance: The B suffix indicates a ±5% tolerance. A part with a tighter tolerance (e.g., ±2%) is acceptable, but a looser one is not recommended for precision circuits.

4. Package: The DO-15 package is standard for this type of diode. Ensure the physical dimensions and lead spacing match for proper mounting.

If Unavailable: In non-critical applications, multiple lower-power Zener diodes (e.g., 1.3W 1N4743A) can be connected in series to achieve both the required voltage and a combined higher power rating, though this is less efficient with board space.

ICGOODFIND: The Onsemi 1N5343BRLG is a high-power, precise component essential for voltage regulation tasks. When selecting this diode or a replacement, engineers must prioritize its 13V clamping voltage, 5W power handling capability, and the critical need for thermal derating to ensure long-term system stability and reliability.

Keywords: Zener Diode, Voltage Regulation, 5W Power Rating, 13V, Shunt Regulator