In the era of rapid development of electronic devices, it is crucial to protect circuits from transient voltage impacts. TVS (Transient Voltage Suppressor) diodes, as a key circuit protection device, play an irreplaceable role. This article will comprehensively elaborate on the definition, characteristics, working principle, application, selection, differences from Zener diodes, and testing methods of TVS diodes. https://www.sic-components.com/tvs-diodes
What is a TVS Diode?
Key Characteristics of TVS Diodes
Fast Response: TVS diodes can respond to transient voltages within an extremely short time (usually in the range of picoseconds to nanoseconds), quickly transitioning from a high-impedance state to a low-impedance state, and promptly bypassing the overvoltage to the ground, providing rapid protection for the circuit.
High Surge Absorption Capacity: It can withstand transient power up to several kilowatts, absorb a large amount of energy, effectively suppress overvoltages, and ensure the normal operation of the circuit under harsh voltage environments.
Low Leakage Current: Under normal operating voltage, the TVS diode is in a high-impedance state, with only a very small leakage current passing through, which has almost no impact on the normal operation of the circuit and ensures the stability and low-power consumption characteristics of the circuit.
Wide Voltage Range: It has various breakdown voltage and clamping voltage specifications, which can be applied to circuit protection requirements of different voltage levels, covering from low-voltage consumer electronic devices to high-voltage industrial application scenarios.
Types of TVS Diodes
Unidirectional TVS Diodes: The function of a unidirectional TVS diode in the circuit is similar to that of a rectifier diode. When it is forward-conducting, it is like an ordinary diode, and when the reverse voltage reaches the breakdown voltage, it will quickly enter the avalanche breakdown state and clamp the transient voltage. It is commonly used in DC power supply circuits, unipolar signal lines, etc., to protect the circuit from forward overvoltages and reverse transient voltages.
Bidirectional TVS Diodes: A bidirectional TVS diode can be equivalent to two unidirectional TVS diodes connected back-to-back. It can protect against transient voltages in both positive and negative directions. It is suitable for AC circuits, bidirectional signal lines, and scenarios where protection against surges in both positive and negative voltages is required, such as data lines and communication interfaces. Compared with unidirectional TVS diodes, its application scenarios are more extensive and flexible.
Working Principle of TVS Diodes
Typical Applications of TVS Diodes
Power Circuit Protection: At the input and output ends of the power supply, TVS diodes can effectively suppress surge voltages from the power grid, transient spikes generated by power switches, etc., protect the power module and various electronic devices connected to the power supply, and ensure the stable operation of the power system.
Communication Interface Protection: In communication interface circuits such as USB, Ethernet, and RS-232, TVS diodes can protect against transient voltages caused by electrostatic discharge, electromagnetic interference (EMI), etc., ensure the accuracy and reliability of data transmission, and prevent interface chips from being damaged due to overvoltages.
Automotive Electronic Systems: During the operation of automobiles, the electrical system will face various complex voltage interferences, such as transient voltages generated by engine ignition and load switching. TVS diodes are widely used in the circuits of automotive electronic control units (ECUs), sensors, in-vehicle communication devices, etc., to protect these key electronic components from voltage impacts and improve the stability and reliability of automotive electronic systems.
Industrial Automation Equipment: In industrial environments, factors such as electromagnetic interference and lightning strikes are likely to cause overvoltage phenomena in equipment circuits. TVS diodes are used in the control circuits, sensor interfaces, motor drive circuits, etc., of industrial automation equipment, which can enhance the anti-interference ability of the equipment and ensure the continuity and safety of industrial production.
Considerations for Selecting TVS Diodes
Breakdown Voltage (VBR): The breakdown voltage of the TVS diode should be selected according to the normal operating voltage of the circuit to ensure that it does not conduct during normal operation and can respond in a timely manner when an overvoltage occurs. Generally, the VBR should be slightly higher than the maximum normal operating voltage of the circuit, leaving a certain safety margin.
Clamping Voltage (VCL): The clamping voltage is the level at which the TVS diode limits the voltage when it withstands transient current. The lower this value is, the better the protection effect for the protected circuit. When selecting, it is necessary to ensure that the VCL is lower than the maximum withstand voltage of the protected component to effectively protect the circuit.
Peak Pulse Power (PPM): According to the energy of the possible transient voltage, select a TVS diode with sufficient peak pulse power to ensure that it can absorb transient energy without being damaged. The PPM should be greater than the maximum power that the transient voltage may generate.
Package Form: TVS diodes have various package forms, such as surface mount package (SOT, SMD, etc.) and through-hole package (DO-41, DO-15, etc.). The selection of the package form needs to consider factors such as the layout of the circuit board, the installation method, and the heat dissipation requirements.
Response Time: For circuits with high requirements for the response speed to transient voltages, a TVS diode with a short response time should be selected to ensure that it can play a protective role in a timely manner when a transient voltage occurs.
Differences between TVS Diodes and Zener Diodes (ZD)
Application Purpose: Zener diodes are mainly used for voltage regulation, using their stable voltage characteristics to provide a constant reference voltage for the circuit within a low current range (usually 5mA - 40mA). In contrast, TVS diodes are mainly used for overvoltage protection, quickly conducting to absorb energy when a transient overvoltage occurs in the circuit to protect the circuit.
Voltage Parameters: Zener diodes focus on the Zener voltage (VZ), which remains relatively stable within the specified low current range. TVS diodes have two important parameters, the reverse stand-off voltage (VRWM) and the breakdown voltage (VBR). The VRWM is the voltage that does not cause breakdown during normal operation, and the VBR is the voltage at which conduction starts for protection. In addition, its clamping voltage (VCL) is used to limit the level of overvoltage.
Current Handling Capacity: Zener diodes are generally not suitable for large current situations and mainly work in small signal circuits. TVS diodes can withstand large transient currents, usually capable of handling currents in the range of several amperes to dozens of amperes to cope with the energy absorption during overvoltage transients.
What is the difference between TVS and Schottky diodes?
Function: Schottky diodes are mainly used for rectification with a low forward voltage drop (e.g., 0.2V - 0.4V), high switching speed, and are suitable for high-frequency applications. TVS diodes are for transient voltage protection, clamping overvoltages and protecting circuits from voltage surges.
Voltage and current handling: Schottky diodes are rated for specific forward and reverse currents and voltages in normal operating conditions. TVS diodes are designed to handle large transient currents during overvoltage events and have specific breakdown and clamping voltage ratings for protection purposes.
Operation principle: Schottky diodes operate based on the Schottky barrier between the metal and semiconductor. TVS diodes operate based on the avalanche breakdown or Zener breakdown principle to protect against overvoltages.
Comprehensive Testing Guide for TVS Diodes
Breakdown Voltage Testing
Testing Equipment: A DC power supply, a current-limiting resistor, a voltmeter, and an ammeter are required.
Testing Steps: Connect the TVS diode in series with the current-limiting resistor to the DC power supply, gradually increase the power supply voltage, and monitor the voltage across the TVS diode with a voltmeter and the current with an ammeter. When the current suddenly increases sharply, the voltage at this time is the breakdown voltage (VBR). Record this value and compare it with the device specification to determine whether it meets the requirements.
Clamping Voltage Testing
Testing Equipment: A pulse generator, an oscilloscope, and a load resistor.
Testing Steps: Use the pulse generator to generate simulated transient voltage pulses and apply them to the circuit connected with the TVS diode and the load resistor. Observe the voltage waveform across the TVS diode through the oscilloscope. The highest voltage value when the TVS diode conducts under the action of the pulse is the clamping voltage (VCL). Check whether this value is within the specified range.
Testing with a Multimeter
Setting the Multimeter: Set the multimeter to the diode testing mode.
Polarity Judgment and Testing: Determine the anode and cathode according to the identification of the TVS diode. Connect the red probe of the multimeter to the anode and the black probe to the cathode. If the diode is normal, the multimeter should display a certain forward voltage drop (about 0.7V for silicon TVS diodes), and some multimeters will beep. Then, exchange the probes and measure the reverse resistance. Under normal circumstances, a high-resistance state (infinite or close to infinite) should be displayed. If the measurement results do not meet the above conditions, it indicates that the TVS diode may be faulty.
Signs of a Bad TVS Diode
Short Circuit: If the TVS diode shows a low-resistance state during both forward and reverse measurements and current can pass freely, it indicates a short circuit and the loss of its protection function.
Open Circuit: If high resistance is displayed during both forward and reverse measurements and no current passes through, it indicates that the TVS diode is open-circuited and unable to protect the circuit.
Performance Degradation: During the testing process, if parameters such as the breakdown voltage and clamping voltage deviate from the range specified in the specification, or the leakage current increases significantly, it indicates that the performance of the TVS diode has degraded and it may not be able to effectively protect the circuit, and it needs to be replaced in a timely manner.
SIC possesses a large quantity of complete and high-quality TVS Diodes(https://www.sic-components.com/tvs-diodes), which can fully meet the protection requirements of various circuits. Its products cover a variety of types, ranging from low-voltage models suitable for low-voltage circuits to high-voltage specifications capable of handling high-voltage environments, and everything in between. In terms of power, whether it is for small-power application scenarios or high-power circuits that need to withstand high pulse power, SIC's TVS Diodes can provide reliable protection. These TVS Diodes adopt advanced manufacturing processes and have the characteristic of rapid response, enabling them to react instantaneously to voltage transients, clamp the voltage at a safe level, and effectively protect sensitive electronic components. With their excellent performance and rich product line, SIC's TVS Diodes become the ideal choice for ensuring the stable operation of circuits in numerous industries.
FQA:
1. What is the difference between TVS and normal diodes?
Function: Normal diodes like rectifier diodes are for rectification, voltage regulation in some cases, and signal processing. TVS diodes are specifically for transient voltage protection, reacting to overvoltage events and clamping the voltage to protect the circuit.
Voltage handling: Normal diodes have a specific forward voltage drop (e.g., about 0.7V for silicon diodes) and are rated for certain forward and reverse voltages. TVS diodes are designed to handle high transient voltages and currents during overvoltage events, with specified breakdown voltages and clamping voltages.
Response time: TVS diodes respond quickly (in the order of picoseconds to nanoseconds) to transient events, while normal diodes have a relatively slower response.
2. Where are TVS diodes used?
TVS diodes are used in various circuits, including power supply circuits to protect from surges and spikes; communication interfaces like USB, Ethernet, and RS - 232 to safeguard against ESD and EMI induced transient voltages; automotive electronics in ECUs, sensors, and in - vehicle communication systems; industrial automation in control circuits, motor drive circuits, and sensor interfaces; and consumer electronics such as smartphones, tablets, and laptops to protect internal circuits from voltage fluctuations.
3. Why not use Schottky diode for transient voltage protection?
Schottky diodes are mainly for rectification, featuring a low forward voltage drop and high switching speed. They are not designed to handle high transient voltages and currents associated with surges and ESD. They lack the ability to clamp transient overvoltages, which is the main function of TVS diodes, so they are not suitable for transient voltage protection in many cases.
4. How are TVS diodes measured?
Electrical parameters: Parameters like breakdown voltage (VBR), clamping voltage (VCL), peak pulse power (PPM), and leakage current are measured. Breakdown voltage is measured by gradually increasing the voltage across the diode until it breaks down. Clamping voltage is measured during the application of a transient voltage pulse, observing the voltage across the diode during conduction. Peak pulse power is related to the energy - handling capacity, and leakage current is measured under normal operating voltage conditions.
Performance in circuits: The performance of TVS diodes in a circuit can be evaluated by simulating transient voltage events (e.g., using a pulse generator to generate surges) and observing how the TVS diode protects the circuit, checking if the protected components are safe from damage.
5. What causes TVS diodes to fail?
Excessive voltage or current: If the transient voltage or current exceeds the rated values of the TVS diode, it can cause damage, such as burnout or short - circuit.
Overheating: Continuous operation under high current or high - power conditions can cause overheating, leading to performance degradation and eventually failure.
Aging: Over time, the performance of TVS diodes may degrade due to aging effects, such as changes in breakdown voltage and clamping voltage.
Electrical stress: Repeated exposure to transient events can cause cumulative damage, gradually reducing its lifespan and protection ability.
6. What happens if a diode has too much current?
Overheating: Excessive current can cause the diode to generate a large amount of heat, potentially leading to thermal damage, such as melting of internal components or degradation of the semiconductor material.
Breakdown: In the case of TVS diodes, if the current exceeds the rated value during a transient event, it can cause abnormal breakdown, potentially leading to a short - circuit or failure of the diode.
Performance degradation: For normal diodes used in rectification or other applications, excessive current can affect their forward voltage drop and reverse leakage current characteristics, degrading their performance over time.
7. How do you choose a TVS diode?
Breakdown voltage: Select a TVS diode with a breakdown voltage slightly higher than the maximum normal operating voltage of the circuit.
Clamping voltage: The clamping voltage should be lower than the maximum withstand voltage of the protected components.
Peak pulse power: Based on the expected transient energy in the circuit, choose a TVS diode with sufficient peak pulse power.
Response time: For circuits with high requirements for response speed to transient voltages, choose a TVS diode with a short response time.
Package form: Consider the layout of the circuit board, installation method, and heat dissipation requirements when choosing the package form.
8. What are the advantages of TVS diodes?
Fast response: TVS diodes can respond quickly to transient voltage events, typically in the picosecond - to - nanosecond range, providing immediate protection to the circuit.
High surge absorption: They can absorb a large amount of transient energy, with high peak pulse power ratings, protecting sensitive components from damage caused by voltage spikes.
Low leakage current: In normal operating conditions, TVS diodes have a very low leakage current, minimizing the impact on the normal operation of the circuit and helping to maintain low power consumption.
Wide voltage range: Available in a variety of breakdown voltage and clamping voltage specifications, TVS diodes can be used in different voltage - level circuits.
Reliable protection: They offer reliable protection against various transient voltage sources such as ESD, lightning strikes, and power supply fluctuations, enhancing the overall reliability of the electronic system.
9. What is the difference between varistor and TVS diode?
Operation principle: Varistors operate based on the change of resistance with voltage. TVS diodes operate based on the avalanche breakdown or Zener breakdown principle of semiconductors.
Response time: TVS diodes generally have a faster response time (picoseconds to nanoseconds) compared to varistors, which may have a response time in the microsecond range.
Voltage and current handling: Varistors can handle relatively large transient currents, but their clamping voltage characteristics may not be as precise as those of TVS diodes. TVS diodes are designed to clamp the voltage at a specific level during overvoltage events.
Application scenarios: Varistors are often used in power supply circuits for general overvoltage protection. TVS diodes are more suitable for protecting sensitive electronic components in communication interfaces, control circuits, and other applications where precise voltage clamping and fast response are required.
10. Can you put TVS diodes in series?
Yes, TVS diodes can be put in series. This is useful in applications where a higher breakdown voltage is required, as the total breakdown voltage of the series combination is the sum of the breakdown voltage.
Hot-selling products of SIC
71421LA55J8 UPD44165184BF5-E40-EQ3-A SST39VF800A-70-4C-B3KE IS66WV1M16DBLL-55BLI-TR AS4C32M16SB-7BIN W25Q16FWSNIG
AS7C34098A-20JIN 752369-581-C W957D6HBCX7I TR IS61LPS12836EC-200B3LI MX25L12875FMI-10G QG82915PL
Product information is from SIC Electronics Limited. If you are interested in the product or need product parameters, you can contact us online at any time or send us an email: sales@sic-chip.com.
Wishlist (0 Items) 