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