Infineon BB439: A Comprehensive Technical Overview and Application Note
The Infineon BB439 is a silicon planar power Zener diode, specifically engineered for voltage regulation and over-voltage protection in a wide array of electronic circuits. As a critical component in the designer's toolkit, it offers precise voltage clamping, robust performance, and high reliability, making it a preferred choice for industrial, automotive, and consumer applications.
Technical Overview
The BB439 is characterized by its nominal Zener voltage (VZ) of 39V, with a tight tolerance of ±5%. This allows for highly accurate voltage reference and regulation. The device is capable of dissipating a maximum power of 1.3W at a case temperature of 75°C, a critical factor for ensuring stability under load. Its excellent linear temperature coefficient ensures stable performance across a wide operating temperature range, typically from -65°C to +175°C.
The diode's construction features a soldered and passivated silicon chip mounted in a hermetically sealed SOD-123FL plastic package. This package offers a compact footprint, which is essential for modern, space-constrained PCB designs, while also providing effective heat dissipation. The low reverse leakage current and dynamic impedance are key parameters that contribute to its efficiency in regulation circuits.
Key Features:
Zener Voltage (VZ): 39V
Power Dissipation (Ptot): 1.3 W
Tolerance: ±5%
Package: SOD-123FL
Application Notes
The primary function of the BB439 is to maintain a constant voltage across a load. Its applications are diverse:
1. Voltage Regulation: It is commonly used as a shunt regulator in power supplies. By placing it in parallel with the load, it clamps the voltage to 39V, diverting excess current away from sensitive components to protect them from over-voltage conditions.
2. Over-Voltage Protection (OVP): In circuits susceptible to voltage spikes, such as those found in automotive systems (e.g., load dump protection) or telecom interfaces, the BB439 acts as a clamping device. It rapidly conducts when the voltage exceeds its breakdown threshold, safeguarding downstream ICs and transistors.
3. Voltage Reference: Its stable characteristics make it suitable for providing a fixed reference voltage in analog circuits, ADC modules, and sensor interfaces where precision is paramount.
When designing a circuit with the BB439, selecting an appropriate current-limiting series resistor (RS) is crucial. This resistor is calculated based on the input voltage (VIN), the desired Zener current (IZ), and the load current (IL). The resistor must be chosen to ensure the Zener operates within its specified power limits to prevent thermal runaway and ensure long-term reliability.
For instance, in a simple regulator circuit with a 50V input, a resistor value must be chosen to set the Zener current (IZ) to a value that keeps the power dissipation (P = VZ IZ) well below the 1.3W maximum, typically derated for elevated ambient temperatures.
In summary, the Infineon BB439 is a highly reliable and precise 39V Zener diode. Its robust construction, stable thermal performance, and compact form factor make it an indispensable component for engineers designing for voltage regulation, reference generation, and critical over-voltage protection in demanding environments.
Keywords: Zener Diode, Voltage Regulation, Over-Voltage Protection, Shunt Regulator, SOD-123FL Package.
