Contents

• Introduction
• General Characteristics of TVS Diodes
• Functions of TVS Diodes
• Basic TVS Diode Topologies

Introduction

• Electrostatic discharge (ESD) occurs when static electricity suddenly discharges. While this may only cause a brief shock to a person, it can be highly damaging to electronic devices. In some cases, an ESD event can permanently destroy electronic components. In others, it may create intermittent faults that are difficult to identify and troubleshoot.
• Although ESD risks can be managed during the design, prototyping, and manufacturing stages, electronic products must also be robust enough to withstand real-world conditions after deployment. While no circuit board can be made completely immune to ESD, proper PCB design practices and dedicated protection components can significantly reduce the risk of damage.
• Transient Voltage Suppression (TVS) diodes are critical protection devices used in modern electronic circuits. They are specifically designed to safeguard sensitive components from voltage spikes and transient surges. These diodes respond extremely quickly to overvoltage events by clamping excessive voltage levels and diverting harmful currents away from vulnerable circuitry.

In this blog, we will explore the general characteristics, key functions, and common topologies of TVS diodes to help you better understand their importance in circuit protection.

General Characteristics of TVS Diodes

TVS diodes possess several unique characteristics that make them highly effective for transient voltage suppression and ESD protection.

Functions of TVS Diodes

TVS diodes perform essential protective functions by limiting transient voltages and redirecting surge currents away from sensitive electronic components.

Basic TVS Diode Topologies

Depending on the application requirements, TVS diodes can be implemented using different circuit topologies to provide effective protection for power, signal, and communication lines.

In this blog, we’ll explore the general characteristics, functions, and basic topologies of TVS diodes to help you understand their role in circuit protection.

1-General Characteristics of TVS Diodes

TVS diodes are specialized semiconductor devices with unique properties that make them ideal for transient suppression.

1.1 Fast Response Time

TVS diodes react almost instantaneously (in picoseconds) to transient events, far faster than other protection devices such as varistors or gas discharge tubes.

1.2 High Surge Current Handling

TVS diodes can handle large surge currents, ranging from a few amperes to several hundred amperes for short durations, making them highly effective against high-energy transient events.

1.3 Low Clamping Voltage

When activated, TVS diodes clamp the voltage to a safe level (V_C – Clamping Voltage), keeping it below the breakdown threshold of the protected components.

1.4 Bidirectional vs. Unidirectional Operation

• Unidirectional TVS Diodes: Protect against positive voltage spikes and are commonly used in DC circuits.
• Bidirectional TVS Diodes: Suppress both positive and negative transient voltages and are typically used in AC circuits.

1.5 Low Leakage Current

Under normal operating conditions, TVS diodes exhibit very low leakage current, ensuring they do not interfere with the performance of the protected circuit.

2-Functions of TVS Diodes

TVS diodes serve two primary functions in electronic circuits, helping protect sensitive components from transient voltage events and surge currents.

2.1 Voltage Clamping

When a transient voltage exceeds the diode’s breakdown voltage (V_BR), the TVS diode enters avalanche mode and clamps the voltage to a safe level (V_C). This prevents excessive voltage from damaging sensitive electronic components.

2.2 Current Diversion

The TVS diode redirects excess current to ground, preventing harmful surge currents from reaching critical devices such as integrated circuits (ICs), microcontrollers, and communication interfaces.

Common Applications

• ESD Protection: Protects USB, HDMI, Ethernet, and other communication ports from electrostatic discharge events.
• Lightning & Surge Protection: Safeguards power lines and telecommunications circuits from lightning-induced surges and transient overvoltages.
• Automotive Electronics: Provides load-dump protection and surge suppression in 12V and 24V vehicle electrical systems.
• Industrial Equipment: Protects sensitive circuits from voltage spikes caused by inductive switching and heavy electrical loads.

3-Basic TVS Diode Topologies

TVS diodes can be implemented in various circuit configurations depending on the application requirements and the level of protection needed.

3.1 Single TVS Diode Protection

In this configuration, a single TVS diode is connected in parallel with the circuit being protected.

• A single TVS diode is placed in parallel with the protected circuit.
• Suitable for low-voltage DC lines (e.g., USB data lines).

3.2 TVS Diode + Series Resistor (For Current Limiting)

A series resistor is added to limit the current during a transient event, reducing the electrical stress placed on the TVS diode.

• A resistor limits the current during a transient event, reducing stress on the TVS diode.
• Used in signal lines where resistance doesn’t affect performance.

3.3 Dual TVS Diodes for Differential Line Protection

This topology uses two TVS diodes to protect differential communication lines from transient voltage events.

• Used in high-speed data lines (e.g., RS-485, CAN bus) to protect against differential transients.
• Two diodes clamp positive and negative transients.

3.4 TVS Array (Multi-Line Protection)

A TVS array integrates multiple TVS diodes into a single package, allowing protection for several input and output lines simultaneously.

• Multiple TVS diodes integrated into a single package for protecting several I/O lines (e.g., HDMI, Ethernet).
• Reduces PCB space and ensures uniform protection.

Conclusion

• TVS diodes play a vital role in protecting modern electronic systems from transient voltage events that can cause permanent damage or unpredictable failures.
• Their extremely fast response time, strong surge current handling capability, and flexible circuit integration options make them an essential solution for ESD protection, surge suppression, and overvoltage safeguarding across a wide range of applications.
• By carefully selecting the appropriate TVS diode type (unidirectional or bidirectional) along with the correct circuit topology, engineers can achieve reliable protection while preserving signal integrity and overall system performance.

Would you like recommendations for specific TVS diode models based on your application? Share your requirements in the comments.