TVS Diode: Transient Voltage Suppression Explained

A Transient Voltage Suppression (TVS) diode is a type of semiconductor device designed to protect electronic components and circuits from voltage spikes and transients. These diodes are solid-state PN junction devices.

Figure 1 shows the symbols used to represent TVS diodes in circuit diagrams.

The surge power and surge current handling capabilities of a TVS diode are directly related to its junction area. A larger cross-sectional area means a higher capacity to absorb transient currents.

The key difference between a TVS diode and a Zener diode is that TVS diodes are specifically designed to suppress transient voltages, while Zener diodes are designed to regulate voltage.

Types of TVS Diodes

There are two main types of TVS diodes:

• Uni-directional: These diodes protect against voltage spikes in one direction only.
• Bi-directional: These diodes can handle voltage spikes in both directions. They are preferred in applications where the polarity of the voltage surge may vary.

Working Principle

TVS diodes work by rapidly clamping the voltage across them when it exceeds a predefined threshold. They have a very fast response time, diverting excess voltage away from the protected circuit, preventing damage to components.

This clamping action is achieved through a combination of the diode’s intrinsic properties and design. Under normal operating conditions, a TVS diode presents a high impedance to the protected circuit. However, when the voltage exceeds the normal level, the TVS diode junction avalanches, providing a low impedance path for the transient current.

This diverts the transient current away from the sensitive components, protecting them. The voltage across the circuit is limited to the TVS diode’s clamping voltage. Once the transient threat vanishes, the diode returns to its high impedance state.

A significant benefit of using a TVS diode is that it doesn’t wear out, and its electrical parameters do not degrade over time.

TVS diodes are available in a wide range of voltages, typically from 5 Volts to 440 Volts. They are used as board-level protectors for semiconductors and other sensitive parts.

Applications

Common applications of TVS diodes include:

• MOS memory protection
• AC power line protection
• Signal and data line protection
• Telecommunication equipment protection

Recent Innovations

Littelfuse Inc. recently launched six new series of highly reliable TVS diodes designed for aerospace applications.

Summary

TVS diodes are primarily used for protection applications, safeguarding sensitive electronic equipment from lightning surges and other unwanted voltage transients.

TVS Diode Manufacturers/Vendors

Here are some popular TVS diode manufacturers and vendors:

• Semtech Corporation
• Digikey
• ON Semiconductor
• Vishay
• Littelfuse Inc.
• Bourns