onsemi 1N5352BG Zener Diode: Key Specifications and Application Circuit Design

The onsemi 1N5352BG is a robust 15V, 5W Zener diode engineered for voltage regulation and protection in a wide array of electronic circuits. Housed in a durable DO-201AD package, this component is designed to handle significant power dissipation, making it a reliable choice for industrial, automotive, and power supply applications.

Key Specifications

The defining electrical characteristics of the 1N5352BG make it suitable for demanding environments. Its paramount specifications include:

Zener Voltage (VZ): 15V ±5% measured at the test current IZT.

Power Dissipation (Ptot): A substantial 5.0 Watts at a case temperature (Tc) of 75°C, derated linearly above this temperature.

Test Current (IZT): 100 mA, the current at which the nominal Zener voltage is specified.

Maximum Zener Impedance (ZZT): 2.5 Ω at IZT, indicating a stable regulation voltage over a range of currents.

Reverse Leakage Current: Typically less than 5 µA at a voltage below the knee of the Zener characteristic curve.

Operating Temperature Range: -65°C to +200°C, ensuring performance under extreme conditions.

Application Circuit Design: A Basic Voltage Regulator

A primary application of the 1N5352BG is to create a simple shunt voltage regulator. The core design goal is to maintain a constant 15V output across a load, even with variations in the input voltage or load current.

Component Selection and Calculations:

1. Input Voltage (VIN): Must be greater than the desired output voltage (VOUT = 15V). A common choice is an unregulated supply like 18V to 24V.

2. Series Resistor (RS): This is the most critical design component. It limits the current through the Zener diode and determines the regulator's operational range.

Purpose: It must supply sufficient current to the Zener and the load while dropping the excess voltage (VIN - VOUT).

Calculation: The value is chosen based on the maximum and minimum input voltages (VIN(max), VIN(min)) and the maximum and minimum load currents (IL(max), IL(min)).

The governing equation is: RS = (VIN(min) - VZ) / (IZ(min) + IL(max))

You must also ensure the resistor's power rating is sufficient: PRS > (VIN(max) - VZ)² / RS

Example: For VIN=24V±10% (21.6V to 26.4V), a 15V output, and a load drawing up to 50mA, RS might be chosen around 33Ω to 47Ω with a power rating of at least 3W.

3. Zener Diode (D1): The 1N5352BG is chosen for its 15V regulation and 5W capability.

Verification: The maximum current through the Zener (when load current is minimum, e.g., 0mA) must be checked to ensure it does not exceed the diode's maximum limits.

IZ(max) = (VIN(max) - VZ) / RS. This power dissipated in the Zener is PZ = VZ IZ(max). This value must not exceed the device's power rating, considering any necessary derating for temperature.

Circuit Operation:

When power is applied, the Zener diode begins to conduct in reverse bias once the input voltage exceeds its 15V breakdown voltage. It then shunts any excess current not required by the load, maintaining a nearly constant 15V potential across its terminals and the load. The series resistor, RS, ensures the current stays within safe operating limits for both the Zener and the power supply.

Enhancements for Real-World Use:

For improved performance, a capacitor (e.g., 10µF to 100µF) can be placed in parallel with the Zener diode to reduce output noise. For more precise regulation or higher current loads, this shunt regulator can be used as a stable reference voltage for an external pass transistor circuit.

ICGOOODFIND: The onsemi 1N5352BG is a high-power Zener diode excelling in simple voltage regulation and transient suppression tasks. Its 5W power rating and 15V breakdown voltage make it ideal for stabilizing voltages in power supplies and protecting sensitive components from over-voltage events. Proper design, particularly the meticulous selection of the series current-limiting resistor, is paramount for ensuring reliable and stable operation within the diode's safe operating area.

Keywords: Zener Diode, Voltage Regulation, Power Dissipation, Shunt Regulator, Circuit Design