If you are an electronic engineer working in the automotive industry, you know how challenging it can be to design and protect circuits that operate in harsh environments. Transient voltage events, such as load dumps, inductive switching, electrostatic discharge (ESD), lightning strike, etc., can cause severe damage to sensitive semiconductor devices, such as microcontrollers, sensors, communication modules, etc. These events can generate voltage spikes that exceed the normal operating range of the circuit, resulting in breakdown, overheating, or even destruction of the devices.

To prevent such catastrophic failures and ensure the reliability and safety of automotive electronics, you need to use transient voltage suppressor (TVS) diodes. A TVS diode is a special type of diode that is designed to protect circuits from transient over-voltage events. Unlike a regular diode that conducts current in one direction only, a TVS diode can conduct current in both directions when the voltage across it exceeds a certain threshold. This way, it can divert or clamp the excess voltage away from the protected circuit and limit the voltage to a safe level.

But how do you choose the right TVS diode for your automotive application? What are the main parameters and characteristics that you need to consider? How do you compare different TVS diode products and select the best one for your specific needs? In this article, we will answer these questions and provide you with some practical examples and guidelines on how to choose the right TVS diode for automotive applications. We will also introduce some of the available TVS diode products from different manufacturers that are suitable for automotive applications and highlight their features and benefits.

By reading this article, you will learn how to protect your automotive circuits from transient over-voltage events using TVS diodes. You will also gain a deeper understanding of the principles and performance of TVS diodes and how to apply them in various automotive scenarios. We hope you find this article informative, interesting and useful for your engineering projects.

Main Parameters and Characteristics of TVS Diodes

---

Before we dive into the details of how to select the right TVS diode for your automotive application, let’s first review some of the main parameters and characteristics of TVS diodes that you need to understand and consider. These parameters and characteristics define the performance and behavior of TVS diodes and determine how well they can protect your circuits from transient over-voltage events.

TVS Diode

Reverse Standoff Voltage (VRWM)

The reverse standoff voltage, also known as the reverse working voltage (VRWM), is the maximum voltage that the TVS diode can withstand in reverse bias without conducting any significant current. In other words, it is the voltage below which the TVS diode behaves like an open circuit and does not affect the normal operation of the protected circuit. The VRWM value is usually specified at a very low leakage current level, such as 1 µA or 5 µA.

The VRWM value is an important parameter to consider when choosing a TVS diode for your automotive application, because it determines the operating voltage range of the protected circuit. Ideally, you want to choose a TVS diode with a VRWM value that is equal to or slightly higher than the maximum normal operating voltage of your circuit. For example, if your circuit operates at 12 V nominal with a tolerance of ±10%, you can choose a TVS diode with a VRWM value of 13.2 V or higher. This way, you can ensure that the TVS diode will not interfere with the normal operation of your circuit and will only activate when a transient over-voltage event occurs.

Reverse Breakdown Voltage (VBR)

The reverse breakdown voltage, also known as the breakdown voltage (VBR), is the minimum voltage that causes the TVS diode to start conducting significant current in reverse bias. In other words, it is the voltage above which the TVS diode behaves like a closed circuit and starts to protect the circuit from transient over-voltage events. The VBR value is usually specified at a low test current level, such as 1 mA or 10 mA.

The VBR value is another important parameter to consider when choosing a TVS diode for your automotive application, because it determines the trigger point of the TVS diode. Ideally, you want to choose a TVS diode with a VBR value that is higher than the maximum normal operating voltage of your circuit but lower than the maximum allowable voltage of your sensitive devices. For example, if your circuit operates at 12 V nominal with a tolerance of ±10% and your sensitive devices can tolerate up to 15 V, you can choose a TVS diode with a VBR value between 13.2 V and 15 V. This way, you can ensure that the TVS diode will not activate during normal operation of your circuit but will activate quickly when a transient over-voltage event occurs.

However, there is one thing to note about the VBR value: it is not a fixed value but rather a range with a wide tolerance. For example, a TVS diode with a nominal VBR value of 15 V may have an actual VBR value anywhere between 13.5 V and 16.5 V depending on manufacturing variations and environmental conditions. Therefore, when choosing a TVS diode based on its VBR value, you need to consider the minimum VBR value rather than the nominal or maximum VBR value. This way, you can avoid choosing a TVS diode that has a lower actual VBR value than your maximum normal operating voltage and may conduct unwanted current during normal operation.

Maximum Clamping Voltage (VC)

The maximum clamping voltage, also known as the clamping voltage (VC), is the maximum voltage that appears across the TVS diode when it is conducting significant current in reverse bias during a transient over-voltage event. In other words, it is the voltage that the TVS diode limits or clamps the transient over-voltage event to protect the circuit from damage. The VC value is usually specified at a high peak pulse current level (IPP) that corresponds to a certain peak pulse power level (PPK) of the transient over-voltage event.

The VC value is perhaps the most important parameter to consider when choosing a TVS diode for your automotive application, because it determines how well the TVS diode can protect your sensitive devices from transient over-voltage events. Ideally, you want to choose a TVS diode with a VC value that is lower than or equal to the maximum allowable voltage of your sensitive devices. For example, if your sensitive devices can tolerate up to 15 V, you can choose a TVS diode with a VC value of 15 V or lower. This way, you can ensure that even during a transient over-voltage event, the voltage across your sensitive devices will not exceed their maximum allowable voltage and they will not be damaged.

However, there is one thing to note about the VC value: it depends on both the VBR value and the IPP value of the TVS diode. The higher the VBR value or the IPP value, the higher the VC value. Therefore, when choosing a TVS diode based on its VC value, you need to consider the worst-case scenario of the transient over-voltage event that your circuit may encounter and choose a TVS diode that can handle the highest possible IPP value at the lowest possible VBR value. This way, you can avoid choosing a TVS diode that has a higher actual VC value than your maximum allowable voltage and may not protect your sensitive devices adequately.

Maximum Peak Pulse Current (IPP)

The maximum peak pulse current, also known as the peak pulse current (IPP), is the maximum current that the TVS diode can conduct in reverse bias during a transient over-voltage event without being damaged. In other words, it is the current that flows through the TVS diode when it is clamping the transient over-voltage event to the VC value. The IPP value is usually specified at a certain peak pulse power level (PPK) of the transient over-voltage event.

The IPP value is another important parameter to consider when choosing a TVS diode for your automotive application, because it determines how much energy the TVS diode can absorb and dissipate during a transient over-voltage event. Ideally, you want to choose a TVS diode with an IPP value that is higher than or equal to the peak pulse current of the transient over-voltage event that your circuit may encounter. For example, if your circuit may encounter a transient over-voltage event with a peak pulse current of 100 A, you can choose a TVS diode with an IPP value of 100 A or higher. This way, you can ensure that the TVS diode will not be damaged by the transient over-voltage event and will continue to protect your circuit.

However, there is one thing to note about the IPP value: it depends on both the VC value and the PPK value of the TVS diode. The lower the VC value or the PPK value, the higher the IPP value. Therefore, when choosing a TVS diode based on its IPP value, you need to consider the worst-case scenario of the transient over-voltage event that your circuit may encounter and choose a TVS diode that can handle the lowest possible VC value at the highest possible PPK value. This way, you can avoid choosing a TVS diode that has a lower actual IPP value than the peak pulse current of the transient over-voltage event and may not protect your circuit adequately.

Peak Pulse Power (PPK)

The peak pulse power, also known as the peak power (PPK), is the maximum power that the TVS diode can handle in reverse bias during a transient over-voltage event without being damaged. In other words, it is the product of the VC value and the IPP value of the TVS diode during a transient over-voltage event. The PPK value is usually specified for a certain pulse shape and duration of the transient over-voltage event, such as 10/1000 µs or 8/20 µs.

The PPK value is another important parameter to consider when choosing a TVS diode for your automotive application, because it determines how much power the TVS diode can handle and dissipate during a transient over-voltage event. Ideally, you want to choose a TVS diode with a PPK value that is higher than or equal to the peak pulse power of the transient over-voltage event that your circuit may encounter. For example, if your circuit may encounter a transient over-voltage event with a peak pulse power of 600 W for 10/1000 µs, you can choose a TVS diode with a PPK value of 600 W or higher for 10/1000 µs. This way, you can ensure that the TVS diode will not be damaged by the transient over-voltage event and will continue to protect your circuit.

However, there is one thing to note about the PPK value: it depends on both the pulse shape and duration of the transient over-voltage event. The shorter the pulse duration or the steeper the pulse rise time, the higher the PPK value. Therefore, when choosing a TVS diode based on its PPK value, you need to consider the worst-case scenario of the transient over-voltage event that your circuit may encounter and choose a TVS diode that can handle the shortest possible pulse duration or the steepest possible pulse rise time. This way, you can avoid choosing a TVS diode that has a lower actual PPK value than the peak pulse power of the transient over-voltage event and may not protect your circuit adequately.

Directionality

The directionality of a TVS diode refers to whether it can conduct current in both directions or only in one direction when the voltage across it exceeds the VBR value. There are two types of TVS diodes based on their directionality: unidirectional and bidirectional.

A unidirectional TVS diode can only conduct current in one direction when the voltage across it exceeds the VBR value. This type of TVS diode is used to protect circuits that operate with a single polarity of voltage, such as 0 to +5 V. The unidirectional TVS diode will protect against both positive and negative transient over-voltage events, but it will conduct immediately for negative transient over-voltage events as it is forward biased.

A bidirectional TVS diode can conduct current in both directions when the voltage across it exceeds the VBR value. This type of TVS diode is used to protect circuits that operate with both positive and negative voltages, such as ±5 V. The bidirectional TVS diode will protect against both positive and negative transient over-voltage events, but it will conduct only when the voltage across it exceeds the VBR value in either direction.

The directionality of a TVS diode is an important parameter to consider when choosing a TVS diode for your automotive application, because it determines how well it can protect your circuit from different types of transient over-voltage events. Ideally, you want to choose a TVS diode with a directionality that matches the polarity of your circuit. For example, if your circuit operates with a single polarity of voltage, such as 0 to +5 V, you can choose a unidirectional TVS diode. If your circuit operates with both positive and negative voltages, such as ±5 V, you can choose a bidirectional TVS diode.

However, there is one thing to note about the directionality of a TVS diode: it may be symmetrical or asymmetrical. A symmetrical bidirectional TVS diode has the same VBR value in both directions. An asymmetrical bidirectional TVS diode has different VBR values in different directions. Therefore, when choosing a bidirectional TVS diode based on its VBR value, you need to consider both the positive and negative VBR values and choose the one that suits your circuit best.

Examples and Guidelines on How to Select the Right TVS Diode for Automotive Applications

---

Now that we have reviewed some of the main parameters and characteristics of TVS diodes, let’s see how we can apply them in various automotive scenarios and how we can compare different TVS diode products and select the best one for our specific needs. In this section, we will provide some examples and guidelines on how to select the right TVS diode for automotive applications such as power supplies, data lines, MOSFET protection, etc.

How to Select the Right TVS Diode for Automotive Applications

Power Supplies

Power supplies are one of the most common and critical applications for TVS diodes in automotive circuits. Power supplies provide the necessary voltage and current for various electronic modules and devices in the vehicle, such as engine control units (ECUs), sensors, communication modules, infotainment systems, etc. Power supplies are also exposed to various transient over-voltage events that can originate from the battery, the alternator, the ignition system, or other inductive loads. Therefore, it is essential to protect power supplies from transient over-voltage events using TVS diodes.

To select the right TVS diode for a power supply application, we need to consider the following parameters and characteristics:

• VRWM: The VRWM value of the TVS diode should be equal to or slightly higher than the maximum normal operating voltage of the power supply. For example, if the power supply operates at 12 V nominal with a tolerance of ±10%, we can choose a TVS diode with a VRWM value of 13.2 V or higher.
• VBR: The VBR value of the TVS diode should be higher than the maximum normal operating voltage of the power supply but lower than the maximum allowable voltage of the sensitive devices powered by the power supply. For example, if the power supply operates at 12 V nominal with a tolerance of ±10% and the sensitive devices can tolerate up to 15 V, we can choose a TVS diode with a VBR value between 13.2 V and 15 V.
• VC: The VC value of the TVS diode should be lower than or equal to the maximum allowable voltage of the sensitive devices powered by the power supply. For example, if the sensitive devices can tolerate up to 15 V, we can choose a TVS diode with a VC value of 15 V or lower.
• IPP: The IPP value of the TVS diode should be higher than or equal to the peak pulse current of the transient over-voltage event that the power supply may encounter. For example, if the power supply may encounter a transient over-voltage event with a peak pulse current of 100 A, we can choose a TVS diode with an IPP value of 100 A or higher.
• PPK: The PPK value of the TVS diode should be higher than or equal to the peak pulse power of the transient over-voltage event that the power supply may encounter. For example, if the power supply may encounter a transient over-voltage event with a peak pulse power of 600 W for 10/1000 µs, we can choose a TVS diode with a PPK value of 600 W or higher for 10/1000 µs.
• Directionality: The directionality of the TVS diode should match the polarity of the power supply. For example, if the power supply operates with a single polarity of voltage, such as 0 to +12 V, we can choose a unidirectional TVS diode. If the power supply operates with both positive and negative voltages, such as ±12 V, we can choose a bidirectional TVS diode.

Data Lines

Data lines are another common and important application for TVS diodes in automotive circuits. Data lines are used to transmit digital signals and data between various electronic modules and devices in the vehicle, such as sensors, communication modules, infotainment systems, etc. Data lines are also exposed to various transient over-voltage events that can originate from ESD, electromagnetic interference (EMI), cross-talk, etc. Therefore, it is essential to protect data lines from transient over-voltage events using TVS diodes.

To select the right TVS diode for a data line application, we need to consider the following parameters and characteristics:

• VRWM: The VRWM value of the TVS diode should be equal to or slightly higher than the maximum normal operating voltage of the data line. For example, if the data line operates at 3.3 V nominal with a tolerance of ±10%, we can choose a TVS diode with a VRWM value of 3.6 V or higher.
• VBR: The VBR value of the TVS diode should be higher than the maximum normal operating voltage of the data line but lower than the maximum allowable voltage of the sensitive devices connected to the data line. For example, if the data line operates at 3.3 V nominal with a tolerance of ±10% and the sensitive devices can tolerate up to 5 V, we can choose a TVS diode with a VBR value between 3.6 V and 5 V.
• VC: The VC value of the TVS diode should be lower than or equal to the maximum allowable voltage of the sensitive devices connected to the data line. For example, if the sensitive devices can tolerate up to 5 V, we can choose a TVS diode with a VC value of 5 V or lower.
• IPP: The IPP value of the TVS diode should be higher than or equal to the peak pulse current of the transient over-voltage event that the data line may encounter. For example, if the data line may encounter a transient over-voltage event with a peak pulse current of 10 A, we can choose a TVS diode with an IPP value of 10 A or higher.
• PPK: The PPK value of the TVS diode should be higher than or equal to the peak pulse power of the transient over-voltage event that the data line may encounter. For example, if the data line may encounter a transient over-voltage event with a peak pulse power of 30 W for 8/20 µs, we can choose a TVS diode with a PPK value of 30 W or higher for 8/20 µs.
• Directionality: The directionality of the TVS diode should match the polarity of the data line. For example, if the data line operates with a single polarity of voltage, such as 0 to +3.3 V, we can choose a unidirectional TVS diode. If the data line operates with both positive and negative voltages, such as ±3.3 V, we can choose a bidirectional TVS diode.

MOSFET Protection

MOSFET protection is another common and important application for TVS diodes in automotive circuits. MOSFETs are widely used in automotive circuits as switches or drivers for various loads, such as motors, lamps, solenoids, etc. MOSFETs are also exposed to various transient over-voltage events that can originate from ESD, inductive switching, load dump, etc. Therefore, it is essential to protect MOSFETs from transient over-voltage events using TVS diodes.

To select the right TVS diode for a MOSFET protection application, we need to consider the following parameters and characteristics:

• VRWM: The VRWM value of the TVS diode should be equal to or slightly higher than the maximum normal operating voltage of the MOSFET. For example, if the MOSFET operates at 12 V nominal with a tolerance of ±10%, we can choose a TVS diode with a VRWM value of 13.2 V or higher.
• VBR: The VBR value of the TVS diode should be higher than the maximum normal operating voltage of the MOSFET but lower than the maximum allowable voltage of the MOSFET. For example, if the MOSFET operates at 12 V nominal with a tolerance of ±10% and can tolerate up to 20 V, we can choose a TVS diode with a VBR value between 13.2 V and 20 V.
• VC: The VC value of the TVS diode should be lower than or equal to the maximum allowable voltage of the MOSFET. For example, if the MOSFET can tolerate up to 20 V, we can choose a TVS diode with a VC value of 20 V or lower.
• IPP: The IPP value of the TVS diode should be higher than or equal to the peak pulse current of the transient over-voltage event that the MOSFET may encounter. For example, if the MOSFET may encounter a transient over-voltage event with a peak pulse current of 50 A, we can choose a TVS diode with an IPP value of 50 A or higher.
• PPK: The PPK value of the TVS diode should be higher than or equal to the peak pulse power of the transient over-voltage event that the MOSFET may encounter. For example, if the MOSFET may encounter a transient over-voltage event with a peak pulse power of 1000 W for 10/1000 µs, we can choose a TVS diode with a PPK value of 1000 W or higher for 10/1000 µs.
• Directionality: The directionality of the TVS diode should match the polarity of the MOSFET. For example, if the MOSFET operates with a single polarity of voltage, such as 0 to +12 V, we can choose a unidirectional TVS diode. If the MOSFET operates with both positive and negative voltages, such as ±12 V, we can choose a bidirectional TVS diode.

Comparison and Selection of Different TVS Diode Products for Automotive Applications

---

One of the challenges of selecting the right TVS diode for automotive applications is that there are many TVS diode products available in the market, each with different parameters and characteristics, such as VRWM, VBR, VC, IPP, PPK, directionality, package type, etc. Moreover, different manufacturers and suppliers may use different naming conventions, test conditions, datasheet formats, etc. for their TVS diode products. Therefore, it can be difficult and time-consuming to compare and select different TVS diode products for automotive applications based on their specifications and performance.

Comparison and Selection of Different TVS Diode Products for Automotive Applications

To overcome this challenge, we can use some tips and tools that can help us compare and select different TVS diode products for automotive applications more easily and efficiently. Here are some of them:

• Use online parametric search tools: Many manufacturers and suppliers provide online parametric search tools that allow us to filter and sort their TVS diode products based on various parameters and characteristics, such as VRWM, VBR, VC, IPP, PPK, directionality, package type, etc. For example, we can use the online parametric search tool from Littelfuse to find their automotive TVS diode products that meet our criteria. We can also use the online parametric search tool from Mouser to find TVS diode products from various manufacturers and suppliers that meet our criteria.
• Use online cross-reference tools: Many manufacturers and suppliers provide online cross-reference tools that allow us to find equivalent or alternative TVS diode products from different manufacturers and suppliers based on their part numbers or specifications. For example, we can use the online cross-reference tool from Nexperia to find equivalent or alternative TVS diode products from Nexperia based on their part numbers or specifications. We can also use the online cross-reference tool from Fuses Unlimited to find equivalent or alternative TVS diode products from various manufacturers and suppliers based on their part numbers or specifications.
• Use online comparison tools: Some manufacturers and suppliers provide online comparison tools that allow us to compare the parameters and characteristics of different TVS diode products side by side. For example, we can use the online comparison tool from STMicroelectronics to compare the parameters and characteristics of up to four TVS diode products from STMicroelectronics side by side.
• Use online selection guides: Some manufacturers and suppliers provide online selection guides that provide recommendations or suggestions on which TVS diode products are suitable for various automotive applications or scenarios. For example, we can use the online selection guide from Diodes Incorporated to find which TVS diode products are suitable for various automotive applications or scenarios based on their power ratings or package types.
• Use datasheets: Datasheets are the most reliable and comprehensive source of information on the parameters and characteristics of TVS diode products. Datasheets also provide graphs and tables that show the performance and behavior of TVS diode products under various test conditions and scenarios. Datasheets also provide application notes and design tips that can help us optimize the use and placement of TVS diode products in our automotive circuits. Therefore, we should always refer to the datasheets of the TVS diode products that we are interested in or have selected for our automotive applications.

To illustrate how to use datasheets to compare and select different TVS diode products for automotive applications, let’s consider an example. Suppose we want to compare and select between two TVS diode products for a power supply application: the PTVS15VP1UP from Nexperia and the SM6T18A from STMicroelectronics. Both TVS diode products have similar parameters and characteristics, such as VRWM, VBR, VC, IPP, PPK, directionality, etc. However, they have different package types: the PTVS15VP1UP comes in the SOD128 package type and the SM6T18A comes in the DO-214AA package type.

To compare and select between these two TVS diode products for our power supply application, we can use their datasheets to find out more information on their parameters and characteristics, such as:

• Package dimensions: The package dimensions of the TVS diode products can affect the board space and layout of our power supply circuit. The datasheets provide the package dimensions of the TVS diode products in millimeters. For example, the PTVS15VP1UP has a package dimension of 3.8 x 4.8 x 1.8 mm and the SM6T18A has a package dimension of 5.8 x 6.7 x 2.6 mm. Therefore, we can see that the PTVS15VP1UP has a smaller package size than the SM6T18A and can save more board space for our power supply circuit.
• Thermal resistance: The thermal resistance of the TVS diode products can affect the heat dissipation and reliability of our power supply circuit. The datasheets provide the thermal resistance of the TVS diode products in degrees Celsius per watt (°C/W). For example, the PTVS15VP1UP has a thermal resistance of 50 °C/W and the SM6T18A has a thermal resistance of 40 °C/W. Therefore, we can see that the SM6T18A has a lower thermal resistance than the PTVS15VP1UP and can dissipate more heat for our power supply circuit.
• Clamping factor: The clamping factor of the TVS diode products can affect the protection level and performance of our power supply circuit. The clamping factor is defined as the ratio of VC to VBR. The lower the clamping factor, the better the protection level and performance of the TVS diode product. The datasheets provide the clamping factor of the TVS diode products at various IPP values. For example, at IPP = 150 A, the PTVS15VP1UP has a clamping factor of 1.46 and the SM6T18A has a clamping factor of 1.58. Therefore, we can see that the PTVS15VP1UP has a lower clamping factor than the SM6T18A and can provide better protection level and performance for our power supply circuit.

Based on this information from their datasheets, we can compare and select between these two TVS diode products for our power supply application based on our preferences and requirements. For example, if we prefer a smaller package size and a lower clamping factor, we can choose the PTVS15VP1UP from Nexperia. If we prefer a lower thermal resistance and a higher power rating, we can choose the SM6T18A from STMicroelectronics.

Conclusions and Recommendations

---

In this article, we have discussed some of the main parameters and characteristics of TVS diodes, such as VRWM, VBR, VC, IPP, PPK and directionality. We have also explained how to choose a TVS diode based on these parameters and characteristics for various automotive applications, such as power supplies, data lines, MOSFET protection, etc. We have also provided some examples and guidelines on how to apply these parameters and characteristics in various automotive scenarios and how to compare different TVS diode products and select the best one for our specific needs. We have also provided some tips and tools on how to compare and select different TVS diode products for automotive applications from various manufacturers and suppliers. We have also illustrated how to use datasheets to compare and select different TVS diode products for automotive applications using an example.

Based on this article, we can draw some conclusions and recommendations on how to select the right TVS diode for automotive applications:

• TVS diodes are essential devices for protecting sensitive electronic equipment from transient over-voltage events in automotive circuits.
• TVS diodes have various parameters and characteristics that determine their protection level and performance in automotive circuits.
• To select the right TVS diode for an automotive application, we need to consider the following parameters and characteristics: VRWM, VBR, VC, IPP, PPK and directionality.
• To select the right TVS diode for an automotive application, we need to match the parameters and characteristics of the TVS diode with the specifications and requirements of the automotive circuit.
• To compare and select different TVS diode products for an automotive application, we can use online parametric search tools, online cross-reference tools, online comparison tools, online selection guides and datasheets.
• To compare and select different TVS diode products for an automotive application, we need to consider the package dimensions, thermal resistance, clamping factor and other factors that may affect the board space, layout, heat dissipation and reliability of the automotive circuit.

We hope this article has been helpful and informative for you. If you have any questions or feedback on this article or on TVS diodes in general, please feel free to contact us. Thank you for reading this article. Have a nice day!