onsemi BZX84C75LT1G Zener Diode: Key Specifications and Application Circuit Design

The BZX84C75LT1G from onsemi is a popular surface-mount Zener diode designed for voltage regulation and protection in low-power circuits. Part of the SOT-23 package family, this component is widely used in portable electronics, communication devices, and precision analog systems due to its compact size, reliability, and well-defined electrical characteristics.

Key Specifications

The BZX84C75LT1G features a Zener voltage (Vz) of 75V with a tolerance of ±5%. This makes it suitable for applications requiring stable reference voltages or overvoltage clamping in higher-voltage circuits. The device operates at a maximum power dissipation of 350mW at temperatures up to 150°C, ensuring robust performance in constrained environments. Its dynamic impedance (ZZT) is typically 70Ω at the test current (IZT) of 5mA, contributing to stable regulation under varying load conditions. The reverse leakage current is minimal (typically <100nA) below the breakdown voltage, enhancing efficiency in precision circuits.

Application Circuit Design

A common use case for the BZX84C75LT1G is as a voltage regulator or shunt protector. In a basic regulator configuration, the diode is placed in parallel with the load, with a series current-limiting resistor to ensure the operating current remains within the specified range (e.g., 1-20mA). For example, in a 100V input circuit, a resistor value can be calculated as:

\[ R = \frac{V_{in} - V_z}{I_z} = \frac{100V - 75V}{5mA} = 5k\Omega \]

This setup clamps the load voltage to 75V, protecting downstream components from overvoltage transients.

Another critical application is in ESD and surge protection. The diode can be connected between a signal line and ground to divert high-voltage spikes, leveraging its fast response time. In multi-voltage systems, it serves as a reference element in comparator or feedback circuits, ensuring stability in power supplies or sensor interfaces.

Design Considerations

- Thermal Management: Ensure power dissipation does not exceed 350mW; derate for high ambient temperatures.

- Current Limiting: Always use a series resistor to avoid exceeding the maximum Zener current (IZM ≈ 20mA).

- Noise and Tolerance: Account for voltage tolerance (±5%) and dynamic impedance in precision applications.

ICGOOODFIND: The onsemi BZX84C75LT1G offers a compact, high-voltage Zener solution ideal for regulation and protection. Its 75V breakdown, low dynamic impedance, and SOT-23 packaging make it a versatile choice for modern electronics designs.

Keywords: Zener Diode, Voltage Regulation, Surge Protection, SOT-23 Package, Dynamic Impedance