onsemi 1N5355BG Zener Diode: Key Specifications and Application Circuit Design
The 1N5355BG from onsemi is a robust 16V, 5W Zener diode designed for voltage regulation and protection in a wide array of electronic circuits. Housed in a durable DO-201AD package, this component is engineered to handle significant power dissipation, making it a reliable choice for demanding industrial, automotive, and power supply applications.
Key Specifications
Understanding the critical parameters of the 1N5355BG is essential for effective circuit design. Its primary specifications include:
Zener Voltage (VZ): 16V (measured at 200 mA, 25°C). There is a tolerance band around this nominal value, which must be considered for precision circuits.
Power Dissipation (Ptot): A substantial 5.0 Watts at (or below) 50°C. This high power rating allows it to stabilize voltages in circuits with higher current flows.
Test Current (IZT): 200 mA. This is the current at which the Zener voltage is specified.
Maximum Zener Impedance (ZZT): 2.5 Ω at IZT. A lower impedance indicates better voltage regulation performance.
Reverse Leakage Current (IR): Typically 50 µA at 12V (a voltage below the breakdown), which is minimal and ensures efficiency.
Operating Temperature Range: -65°C to +200°C, ensuring reliability under extreme environmental conditions.
Application Circuit Design: A Basic Voltage Regulator
A fundamental application of the 1N5355BG is to create a simple shunt voltage regulator. The primary function of this circuit is to maintain a constant output voltage across a load, even with variations in the input voltage or the load current itself.
Component Selection and Calculations:
1. Input Voltage (VIN): Must be higher than the Zener voltage. For a 16V output, a VIN of 18V to 24V is a common choice.
2. Series Resistor (RS): This resistor is crucial as it limits the current through the Zener diode.
Purpose: It drops the excess voltage from the supply and sets the maximum current, protecting the diode from exceeding its power rating.
Calculation: The value of RS is calculated based on the maximum input voltage (VIN(max)), the minimum required load current (IL(min)), and the Zener voltage (VZ).
The current through RS is the sum of the Zener current (IZ) and the Load current (IL): ITotal = IZ + IL.
The voltage drop across RS is VIN - VZ.
The resistor value is calculated as: RS = (VIN(min) - VZ) / (IZ(min) + IL(max))
Power Rating of RS: The resistor must be sized to handle the power it will dissipate: PRS = (VIN(max) - VZ)² / RS
3. Zener Diode (D1): The 1N5355BG is chosen for its 16V regulation and 5W power handling. The maximum current it can handle is IZ(max) = Ptot / VZ = 5W / 16V ≈ 312 mA.
How the Circuit Works:
When the input voltage exceeds 16V, the Zener diode begins to conduct in reverse bias, "clamping" the voltage across it to approximately 16V. Any variation in input voltage or change in load current causes a corresponding change in the current flowing through the Zener diode (shunt current), thereby maintaining a nearly constant voltage across the load. If the load current decreases, the Zener current increases to compensate, and vice versa.
Design Considerations:
Load and Line Regulation: The performance depends on the Zener impedance; a lower ZZT provides better regulation.
Temperature Dependence: The Zener voltage drifts with temperature, which must be accounted for in precision applications.
Efficiency: Shunt regulators are less efficient than linear regulators for high current differences, as the Zener diode constantly draws current.
ICGOOODFIND: The onsemi 1N5355BG is a high-power, reliable Zener diode ideal for simple voltage regulation and transient suppression tasks. Its 5W power rating and 16V breakdown voltage make it exceptionally suited for stabilizing voltages in power supplies and protecting sensitive components from overvoltage events. Proper selection of the series current-limiting resistor is paramount to ensure stable operation and long-term reliability.
Keywords: Zener Diode, Voltage Regulation, Power Dissipation, Circuit Design, Shunt Regulator
