onsemi 1SMB5947BT3G 16V Zener Diode: Datasheet, Pinout, and Application Circuits

The 1SMB5947BT3G from onsemi is a high-power Zener diode designed for voltage regulation and protection in a compact, surface-mount package. This component is part of the popular 1SMB series, known for its ability to dissipate significant power, making it suitable for a wide range of industrial, automotive, and consumer applications. This article provides a detailed look at its datasheet specifications, pinout configuration, and typical application circuits.

Datasheet Overview and Key Specifications

The 1SMB5947BT3G is a 16V Zener diode with a nominal Zener voltage (Vz) of 16V at the test current (IZT). Its primary function is to maintain a constant voltage across its terminals when operated in its reverse breakdown region.

Key electrical characteristics from the datasheet include:

Zener Voltage (VZ): 16V (at IZT = 45.5 mA)

Power Dissipation (Ptot): 3.0 Watts at 50°C, a remarkably high value for a surface-mount device (SMD). This is its most significant advantage.

Maximum Reverse Leakage Current (IR): 5.0 µA (at VR = 12.2V)

Zener Impedance (ZZT): 2.5 Ω (at IZT)

Operating Junction Temperature (TJ): -65°C to +150°C

The device is housed in the DO-214AA (SMB) package, which offers a good balance between size and thermal performance. It is also qualified for AEC-Q101 for automotive applications, ensuring high reliability and performance under stringent conditions.

Pinout and Package Information

The 1SMB5947BT3G is a two-terminal device with a simple anode and cathode configuration. The SMB package is polarized, and identifying the correct orientation is critical for proper circuit operation.

Cathode (K): This terminal is typically marked by a color band on the body of the diode. It is the end that must be connected to the more positive voltage potential for reverse bias operation.

Anode (A): This is the unmarked terminal and must be connected to the more negative voltage potential.

The physical package is designed for surface-mount technology (SMT) and provides a robust structure for handling high power pulses.

Application Circuits

The high power rating of the 1SMB5947BT3G makes it ideal for circuits requiring robust overvoltage protection and voltage regulation.

1. Overvoltage Protection / Transient Suppression

A primary application is protecting sensitive integrated circuits (ICs) from voltage spikes on power supply lines (e.g., from inductive load switching or ESD). The Zener diode is placed in a shunt configuration, parallel to the load and the IC it is protecting.

How it works: Under normal operating conditions (VSUPPLY < 16V), the Zener is in a high-impedance state (reverse leakage) and does not conduct. If a voltage spike occurs that exceeds the 16V breakdown voltage, the diode clamps the voltage to approximately 16V by shunting the excess current to ground, thereby protecting the downstream components. A series resistor is often used to limit the current through the Zener.

2. Simple Voltage Regulator

While not as efficient as linear regulators (LDOs) for primary power regulation, Zener diodes provide a simple and cost-effective solution for generating a stable reference voltage or powering small loads.

How it works: The circuit consists of a series current-limiting resistor (RS) and the 1SMB5947BT3G Zener diode in shunt with the load. The resistor RS is calculated to ensure the Zener current (IZ) is between its minimum (IZK) and maximum (derived from Pmax) values over the expected input voltage and load variations. This maintains a regulated 16V output across the load.

ICGOODFIND Summary

The onsemi 1SMB5947BT3G stands out as an exceptionally robust surface-mount solution for voltage clamping and regulation. Its ability to handle 3W of power dissipation in the compact SMB package makes it a superior choice for demanding environments, including automotive electronics, where suppressing high-energy transients is critical. Its simple two-pin design and well-defined characteristics allow for easy implementation in various circuit protection schemes.

Keywords:

Zener Diode

Voltage Regulation

Overvoltage Protection

Surface-Mount Device (SMD)

Power Dissipation