TVS Diodes (ESD Protection Devices)Section 3　“TVS Diodes (ESD Protection Devices)”

The main function of an TVS Diodes is to enable ESD that enters a device to escape to ground. If there is no TVS Diode, ESD which has a voltage of several thousand volts will be applied directly to the internal ICs.

When an TVS Diodes is installed between an external interface and an IC in order to protect the IC, the input to the IC will be grounded via the TVS Diodes, enabling ESD to escape to ground. Under the normal drive voltage (several volts), the IC is isolated from ground, so data communication is not impaired. The ability to ground an IC circuit when several tens to thousands of volts are applied to it, and also to isolate it from ground when several volts are applied to it, is a necessary function of an TVS Diodes.

The following graph shows the difference between the voltages at the IC side depending upon whether or not an TVS Diodes is installed. Here, an 8 kV ESD is generated using an ESD gun containing a capacitor and internal resistance, and the voltage after it has passed through the device is measured using an oscilloscope. From the waveform of the graph, it can be seen that the existence of the TVS Diodes greatly reduces the voltage applied to the IC side.

A TVS diode is a type of Zener diode.
The difference between a constant voltage diode and a TVS diode is that while a constant voltage diode is used to stabilize the voltage, a TVS diode is used to prevent transient voltages such as ESD.
In addition, while ESD-related specifications are listed for a TVS diode as shown in the items in the red frame below, such specifications are not listed for a constant voltage diode.

The following is a comparison of the differences between varistors, suppressors, and TVS diodes according to each item.

Varistors are often used in power supply ports and data lines.While high capacitance products are superior for their high discharge characteristic, it is challenging to use them at a low capacitance of 0.5pF or less, and the inability to use them in high output RF ports is a disadvantage.

Suppressors are used in Wi-Fi®, Bluetooth®, and other high output RF ports and data lines.With an extremely low capacitance of 0.1pF or less, suppressors are suited to high-speed signal lines.
At the same time, they also have the disadvantage of not discharging at a low voltage.

TVS diodes are used for ESD protection in data lines such as power supply ports and USB, low output power RF ports such as NFC, and RF ports for receive-only GPS, etc.
They cannot be used in high output RF ports like suppressors, but they provide the significant benefit of a fast response time when ESD intrudes due to their high discharge characteristic.

Watch this video to learn more about why TVS diodes are necessary, how they are used, and the features of Murata’s TVS diodes.

Murata's TVS diodes have high static electricity suppression performance. We provide products that support applications ranging from DC to high-speed transmission as well as compact products that help reduce the substrate area.