How to Choose the Right TVS Diode to Protect Complex Circuits
A major aspect of system protection for complex circuits in an unreliable industrial environment is the selection of the right TVS Diode.
Circuits are designed to handle a specific voltage limit, within which they operate safely and in optimal condition. But when this voltage is exceeded, the signal lines and interfaces and the product or function can get damaged. Disturbances from exposure to high transients, voltage or current surges, and more can all negatively affect the performance of a circuit. Fortunately, utilizing the right TVS Diodes can protect sensitive circuit components and systems from electrical overstress caused by power surges, lightning strikes, or nearby machinery. So, let’s take some time to discuss the working principles of TVS Diodes and how they protect your circuits.
Transients are surges in either voltage or current that last for a short time in a circuit, and they can damage the system in several ways. Some transients can be repetitive, while others occur only once. Still, the intensity and amount of time it takes for the transient to happen can vary significantly. Several internal and external factors can trigger spikes and overvoltage events in an electrical circuit.
Diodes are electronic or semi-conductor devices mostly used in power circuits or electronic designs such as rectifiers, inverters, regulators, etc. They conduct current by allowing current to pass through them in one direction. This is the property of diodes that makes them necessary in several applications.
The basic types of diodes are:
- Rectifier (common) Diode
- Zener Diode
- Schottky Diode
However, there’s yet another kind of special diode: the TVS Diode.
A Transient Voltage Suppressor (TVS) Diode is a protection device that is commonly used in power circuits to provide immunity to electrostatic discharge (ESD) and voltage surges.
The typical process to deal with overvoltage in a circuit is to connect these protection devices in parallel with the power circuit to be able to protect the system should a voltage surge occur. In normal voltage situations, TVS Diodes work like an open circuit. When the normal voltage is exceeded, the TVS Diode junction conducts, causing diversion of overvoltage from the secured circuit and then as current is shunted through the clamp diode.
Mainly used to protect semiconductors in a circuit and sensitive devices, the transient voltage suppressor diodes are also used to protect secondary power and signal circuits.
Due to their response speed, accurate voltage, low clamping voltage, and many other merits, TVS Diodes are applied in fields where protection devices are extremely crucial – for example in aerospace, defense, medical and telecommunications.
Three Applications of TVS Diodes for Complex Electrical Circuits
TVS Diodes offer protection to your circuits and have a multitude of different current ratings and their protective abilities increase as the junction area they are made with increases, making it easier for them to absorb higher transient currents. They are specifically designed to suppress transient voltages of varying currents. Apart from this benefit, there are other reasons you should consider choosing a TVS semiconductor to protect your complex circuits.
1. The ability to shield a circuit system against overvoltage and excessive current
A TVS Diode works consistently to protect your circuit from heat during operation. The diode helps to reduce the amount of heat generated and extend the service life of the circuit by reducing any transient operating voltage of the semiconductors and ICs. When the voltage in a circuit is raised above its upper design range, an overvoltage event (such as a voltage spike) occurs, leading to a power surge and considerable damage to devices. In such a situation, the TVS Diode acts as overvoltage protection mainly to prevent electronic components from damage and electronic discharge.
- They work as voltage clamps to limit transient overvoltage
TVS Diodes clamp transient voltage to reduce the amplitude of transients across a circuit system. As a clamping device limiting the voltage to a fixed level, clamp diodes start clamping immediately after the present threshold voltage is increased beyond the set limit. The diode absorbs the excessive voltage to guard the circuit, and when the induced voltage surpasses the avalanche breakdown voltage, the TVS Diodes will absorb the excess energy of the overvoltage. When the overvoltage drops to normal or below the preset voltage threshold level, the diodes reverts to a non-conducting mode.
- Bringing amplitudes to the most controllable level
A protection device must act fast to control both current and voltage in an electrical circuit. TVS semiconductors respond very quickly to stimuli to control amplitudes. The reason is that they’re solid-state diodes that absorb the sudden or momentary effects of an overvoltage by regulating amplitudes and bringing them to a safe level. They offer a wide range of protection that is within the safe operating area to provide quick protection against excessive voltage and current. These diodes form an important part of the protective devices for essential semiconductor components to limit the amplitudes and protect the circuits.
Though it’s crucial to have solid protection for circuits in environments characterized by the presence of hot-pluggable interfaces and where lightning strikes, the best way for surge protection is to use TVS semiconductors to clamp overvoltages to a protected level at the input to the circuit system. It is important to select the appropriate TVS device that suits a given electric application. There is the need for a user or the electrical engineer to carefully understand the distinct functions that a particular type of transient voltage device provides. A careful choice of the device helps to enhance the functionality of the protective device.
Parameters to Consider when Choosing a TVS Diode
Choosing the right TVS Diode to power complex circuits and the relevant differentiators to consider has always been an issue for producers of electronic items. Let’s examine the parameters you need to quickly and accurately select the best transient suppressor.
- Circuit Operating Requirements
One of the core consideration when determining the most suitable circuit protective device is the circuit operating requirements of the electronic application. It is critical to understand the nature of the circuit that the diode powers and helps to protect.
In essence, the operating requirements of the application’s circuit will include the maximum steady-state voltage that has been defined, the optimal ambient temperature recommended and the electric current values and capacities of the electric load of a circuit.
- Clamping Voltage (VC)
Voltage clamping plays a significant role in limiting the amplitude of an electric transient across a circuit to a given threshold. Therefore the circuit protective device will begin conducting when the maximum threshold voltage that has been preset is exceeded. The device will cease conducting and return back to a non-conducting mode when the overvoltage scenario drops below the maximum preset threshold. This process ensures that the overvoltage surges have been successfully clipped off to safe levels.
- Breakdown Voltage Level (VBR)
Sometimes referred to as peak reverse standoff voltage, this is the fault current level whereby the transient suppressor component can safely divert incidences of overvoltage without necessarily interrupting the flow of the electric current. One advantage of TVS diodes is their ability to continue conducting electric current even after the voltage flowing across the diodes significantly drops below the preset breakdown voltage level.
Generally, any circuit protective device will have a preset breakdown voltage level. This is the control level of voltages in electrical circuits. When determining the suitable breakdown voltage it is imperative to ensure that the maximum breakdown voltage is higher than the maximum rated standoff level. On the other hand, care should be taken to ensure that the maximum breakdown voltage does not exceed the absolute maximum rating for the output capacitors.
The breakdown voltage is usually measured as a test current (IT) of 1mA or 10mA. When selecting the appropriate transient suppressor component, it is important to consider this parameter in relation to the electronic application which will use the diode.
- Rated standoff voltage (VWM)
Also commonly referred to as rated or maximum working peak voltage, this is the normal operating voltage specified for a device. When the electric voltage rises to this point the device will begin acting as an impedance so that it could protect the circuit from a high electric current that could cause damage. In normal circumstances, it is usually 10% below the maximum breakdown voltage hence it helps to minimize incidences of standby leakage current.
- Peak impulse current (lPP)
This is the maximum current that a protective device can withstand without getting damaged. When selecting a suitable transient suppressor, it is critical to specify the peak impulse capability for a given transient waveform. In most diodes, the peak pulse capability will be rated either 8/20µs or 10/1000µs impulse waveform.
- Peak Pulse Power Dissipation (PPP)
The actual power dissipation of the transient suppressor component is a key determinant that should be considered when selecting the most suitable circuit protective device for your electronic application. It is calculated by multiplying the peak impulse current by the clamping voltage.
Sample Data Sheet Showing Ratings & Characteristics
Guide for Choosing the Right TVS Diode by MDE Semiconductor, Inc.
Choosing the ideal TVS diode begins with defining the requirements for protection; whether primary design or broad-base protection.
When selecting the product, simply check the Reverse Standoff Voltage (VRWM) or Reverse Working Voltage (VWWM), which is the maximum peak voltage or highest of the normal direct current operation in the circuit. It is vital to determine the circuit’s optimum clamping voltage and leverage a TVS semiconductor that is armed to absorb the high voltage effects that may happen.
In essence, choosing the right TVS Diode depends on several key factors. This guide by MDE Semiconductor, Inc. serves to help you select the best components for your circuit system.
If you’d like to speak with our engineers to determine the proper TVS Diode for your circuit, or to customize an assembly built to your specific designs for board level surge protection device schemes, contact us here.