TVS Diodes: The Versatile Solution for Circuit Protection

What is TVS diode ?

TVS (Transient Voltage Suppression) diode is a type of electronic component designed to protect electronic circuits from voltage spikes or transients. Voltage spikes can occur due to a variety of reasons, including lightning strikes, electrostatic discharge, or switching of inductive loads.

Working of TVS diode ?

TVS diodes work by responding quickly to voltage spikes or transients that may damage electronic circuits. When a voltage spike occurs, the TVS diode begins to conduct current, providing a low-resistance path to ground. This diverts the excess current away from the protected circuit and limits the voltage to a safe level.

The TVS diode is designed to have a very high breakdown voltage, which is the voltage at which it starts to conduct current. This allows it to protect against very high voltage spikes, which could otherwise damage the electronic circuit.

When the voltage spike is over, the TVS diode returns to its high-impedance state, allowing normal operation of the protected circuit. The response time of a TVS diode is typically very fast, on the order of nanoseconds, which ensures that it can respond quickly to voltage spikes.

Type of TVS diode

There are two main types of TVS diodes: unidirectional and bidirectional.

Unidirectional TVS diode

Unidirectional TVS diodes are designed to protect against voltage spikes in one direction only, typically in the forward direction. These diodes have a single PN junction and are designed to conduct when the voltage across the junction exceeds the breakdown voltage. They are commonly used in applications where the voltage is expected to be unidirectional, such as in power supplies.

Bidirectional TVS diode

Bidirectional TVS diodes, on the other hand, are designed to protect against voltage spikes in both directions, both in the forward and reverse directions. These diodes have two PN junctions in parallel, and they can conduct current in either direction when the voltage across either junction exceeds the breakdown voltage. They are commonly used in applications where the voltage can be either polarity, such as in telecommunications and automotive applications.

Selecting the right TVS diode

 TVS diode for a particular application requires consideration of several factors. Here are some steps to follow when selecting a TVS diode:

1. Transient voltage level: The TVS diode must have a breakdown voltage (VBR) that is greater than the expected transient voltage level. This ensures that the TVS diode will conduct and limit the transient voltage to a safe level.
2. Peak pulse current: The TVS diode must have a peak pulse current (Ipp) rating that is greater than the expected peak current of the transient event. This ensures that the TVS diode will be able to handle the current without damage.
3. Clamping voltage: The clamping voltage (Vc) of the TVS diode should be as low as possible to limit the transient voltage to a safe level. The clamping voltage is the voltage level that the TVS diode limits the transient voltage to.
4. Response time: The TVS diode should have a fast response time to ensure that it can quickly clamp the transient voltage and protect the circuit. The response time is the time it takes for the TVS diode to start conducting after the transient voltage exceeds the breakdown voltage.
5. Operating temperature: The TVS diode should be able to operate at the expected temperature range of the application without being damaged.
6. Package and mounting: The TVS diode package and mounting should be suitable for the application, taking into consideration factors such as board space, lead style, and mounting method.

Here is the example of SMAJ33A

 The key parameters for the SMAJ33A TVS diode:

• Breakdown Voltage (VBR): 36.7 – 40.6V
• Peak Pulse Power Dissipation (PPPM): 400W
• Peak Pulse Current (IPP): 14.5A
• Clamping Voltage (VC): 53.3V
• Reverse Standoff Voltage (VWM): 33V
• Operating Temperature Range: -55°C to +150°C
• Package Type: SMA (Surface Mount Axial)

What are different package of TVS diodes

TVS diodes are available in various package types to suit different application requirements. Here are some of the most common package types:

1. Axial package: Axial TVS diodes are cylindrical in shape, with leads at each end. They are typically used in through-hole mounting applications and are available in a range of sizes.
2. Radial package: Radial TVS diodes are similar in shape to axial diodes, but the leads are located at the base of the cylinder. They are also commonly used in through-hole mounting applications.
3. SMD (Surface Mount Device) package: SMD TVS diodes are designed for surface-mount applications and are available in various package sizes, such as SOD (Small Outline Diode), SOT (Small Outline Transistor), and DFN (Dual Flat No-Lead).
4. DO (Diode Outline) package: DO TVS diodes are available in various sizes and are designed for surface-mount and through-hole mounting applications.
5. Power package: Power TVS diodes are designed for high-power applications and are available in various package types, such as TO-92, TO-220, and TO-247.

Commonly used TVS diodes series

Here are some of the most commonly used TVS diodes:

1. 1.5KE Series: The 1.5KE series is a popular axial TVS diode that is commonly used in protection circuits for automotive, telecommunications, and industrial applications. It has a peak pulse power rating of up to 1.5 kW and a breakdown voltage ranging from 6.8 V to 440 V.
2. P6KE Series: The P6KE series is another axial TVS diode that is widely used in various applications, including power supplies, telecom equipment, and industrial controls. It has a peak pulse power rating of up to 600 W and a breakdown voltage ranging from 6.8 V to 440 V.
3. SMBJ Series: The SMBJ series is a popular surface-mount TVS diode that is commonly used in protection circuits for consumer electronics, automotive, and telecom applications. It has a peak pulse power rating of up to 600 W and a breakdown voltage ranging from 5 V to 440 V.
4. SMCJ Series: The SMCJ series is another surface-mount TVS diode that is widely used in various applications, including power supplies, telecom equipment, and automotive electronics. It has a peak pulse power rating of up to 1.5 kW and a breakdown voltage ranging from 5 V to 440 V.
5. DFN10-2L Series: The DFN10-2L series is a small surface-mount TVS diode that is commonly used in portable electronics, such as smartphones and tablets. It has a peak pulse power rating of up to 300 W and a breakdown voltage ranging from 3.3 V to 36 V.

PCB guideline for TVS diode

When designing a PCB layout for a circuit that uses TVS (Transient Voltage Suppression) diodes, there are some guidelines to keep in mind to ensure effective protection and proper functionality:

1. Choose the appropriate TVS diode package: Select a package that fits your PCB footprint and can handle the expected voltage and current levels.
2. Place the TVS diode as close as possible to the protected components: The TVS diode should be placed as close as possible to the input/output pins that need protection to minimize the length of the trace and reduce the risk of voltage overshoot.
3. Ensure adequate trace width: The traces between the TVS diode and the protected components should be wide enough to handle the expected current levels without causing voltage drop or thermal stress.

TVS diode equations

1. Clamping Voltage Equation: The clamping voltage equation for a TVS diode is as follows:

Vc = VBR + (Ip x Rs)

Where:

• Vc is the clamping voltage in volts
• VBR is the breakdown voltage in volts
• Ip is the peak pulse current in amperes
• Rs is the series resistance in ohms

2. Breakdown Voltage Equation: The breakdown voltage equation for a TVS diode is as follows:

VBR = K x Vz

Where:

• VBR is the breakdown voltage in volts
• K is the breakdown voltage ratio (typically around 1.5 to 2.5)
• Vz is the Zener voltage in volts

3. Zener Voltage Equation: The Zener voltage equation for a TVS diode is as follows:

Vz = Vf + (Rs x Iz)

Where:

• Vz is the Zener voltage in volts
• Vf is the forward voltage drop in volts
• Rs is the series resistance in ohms
• Iz is the Zener current in amperes

Advantage of TVS diodes

The main advantage of TVS (Transient Voltage Suppressor) diodes is their ability to protect electronic circuits from overvoltage transients. Here are some of the advantages of using TVS diodes:

1. Fast response time: TVS diodes have a very fast response time, typically on the order of nanoseconds, which allows them to quickly clamp the transient voltage and protect the circuit.
2. High surge current capability: TVS diodes are designed to handle high surge currents, which makes them well-suited for protecting against high-energy transient events.
3. Low clamping voltage: TVS diodes have a low clamping voltage, which means that they limit the transient voltage to a very low level, typically just a few volts above the normal operating voltage of the circuit.
4. Repeatable performance: TVS diodes have a very repeatable clamping voltage and response time, which ensures that they will provide consistent protection over multiple transient events.
5. Low leakage current: TVS diodes have a low leakage current, which means they do not draw significant power from the circuit when not in use.

Disadvantage of TVS diodes

While TVS (Transient Voltage Suppressor) diodes offer many advantages, there are also some disadvantages to consider. Here are a few potential drawbacks:

1. Limited lifetime: TVS diodes have a limited lifetime and can be damaged or degraded by repeated transient events. This means that they may need to be replaced periodically in high-transient environments.
2. Voltage and current limitations: TVS diodes are designed to protect against specific voltage and current levels, and may not be suitable for all applications. It is important to carefully select a TVS diode with appropriate voltage and current ratings for the specific application.
3. Heat dissipation: TVS diodes can generate heat during transient events, which may need to be dissipated to prevent damage to the TVS diode or surrounding components. This may require additional thermal management considerations in the circuit design.
4. Reverse bias limitations: TVS diodes are designed to operate in the forward direction, and may not be effective in protecting against reverse voltage transients. Additional protection may be required for reverse voltage transients.
5. Cost: TVS diodes can be more expensive than other types of voltage protection devices, such as zener diodes or metal oxide varistors (MOVs). However, the cost may be justified in applications where high reliability and fast response times are critical.

Applications of TVS diodes

Here are some common applications of TVS diodes:

1. Protection of electronic circuits in telecommunications equipment, such as modems, routers, and switches.
2. Protection of power supplies, including AC/DC and DC/DC converters, against voltage surges caused by lightning strikes, electrostatic discharge (ESD), or switching transients.
3. Protection of automotive electronics against voltage transients and load dump events.
4. Protection of industrial and automation control systems against electrical noise, power surges, and other voltage transients.
5. Protection of consumer electronics, such as computers, laptops, and smartphones, against voltage surges and ESD.
6. Protection of LED lighting systems against transient overvoltage events.
7. Protection of sensitive electronic components, such as integrated circuits and microprocessors, against voltage surges and electrostatic discharge.
8. Protection of power transmission and distribution systems against lightning strikes and other voltage transients.

Conclusion

In conclusion, TVS (Transient Voltage Suppressor) diodes are an important component in electronic circuits, providing effective protection against transient voltage spikes and surges that can damage or destroy sensitive electronic components. TVS diodes can be used in a wide range of applications, including telecommunications equipment, power supplies, automotive electronics, industrial and automation control systems, consumer electronics, LED lighting systems, and power transmission and distribution systems.

While TVS diodes offer many advantages, such as fast response times and high reliability, there are also some limitations to consider, such as limited lifetime, voltage and current limitations, heat dissipation, reverse bias limitations, and cost. It is important to carefully consider the suitability of TVS diodes for a specific application and to select a TVS diode with appropriate voltage and current ratings, package type, and other performance characteristics.

Frequently asked questions

What is the difference between Zener and TVS diode?

While both Zener and TVS diodes are used for voltage regulation, Zener diodes are typically used for low-power applications and have a fixed breakdown voltage, while TVS diodes are used for high-power applications and have a nonlinear voltage-current characteristic that allows them to handle transient voltage spikes and surges.

What causes a TVS diode to fail?

Here are some common reasons why TVS diodes can fail:

1. Overvoltage conditions
2. Excessive power dissipation
3. Temperature extremes
4. Reverse bias conditions
5. Physical damage

What kind of diode is a TVS?

A TVS (Transient Voltage Suppression) diode is a type of diode that protects electronic circuits from high voltage transients by clamping the voltage to a safe level. They are designed to react quickly to voltage surges and are commonly used in electronics to protect sensitive components.

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