TVS Diodes

Basic Structure	Symbol	Applications and Features
*In the case of single direction		Protects later-stage ICs from unexpected surges caused by static electricity and power supply fluctuations. Typically utilizes the operating principle of constant voltage (Zener) diodes

An acronym for Transient Voltage Suppressor, TVS is designed for overvoltage and ESD protection.

TVS Diode Operation

TVS diodes are devices used to protect downstream ICs from unexpected overvoltages and surges caused by static electricity and power supply fluctuations.
In contrast to rectifier and Schottky barrier diodes that use forward characteristics, TVS diodes (like Zeners) take advantage of the reverse characteristics.
By placing the TVS diode in parallel with the IC as shown in the figure below, the diode operates normally in the OFF state, consuming only a certain amount of leakage current.
When an overvoltage such as surge occurs, the IC turns ON and clamps the overvoltage by allowing the pulse current to be consumed on the TVS side, protecting the subsequent stage IC.

TVS Diode Polarity (Unidirectional and Bidirectional)

The polarity of the TVS diode is a parameter related to circuit quality.
While unidirectional TVS is used as a protection element in LH and other single-pole circuits, it is not suitable for protecting bipolar circuits.
In contrast, bidirectional TVS can protect both the positive and negative poles, making it suitable for protecting data lines in bipolar circuits, CAN, and the like.
Bidirectional TVS can also be used to protect single-pole circuits.

Differences Between TVS and ZD

While TVS and ZD both take advantage of the reverse characteristics of the diode, ZD is mainly utilized for constant voltage applications, so the Zener voltage（V_Z）is specified in the low current range of 5mA to 40mA where the voltage is stable.
What’s more, it is typically used in the ON state.
For TVS, it is important to have breakdown voltage in the event sudden overvoltage such as surge is applied while also operating in the normally OFF state to prevent interference with the IC’s drive voltage.
As a result, there are two specified voltages for standoff（V_RWM）and breakdown（V_BR）, which are voltages that never cause breakdowns.
And since overvoltage protection is the main application, high current in the range of several A to tens of A are listed as part of the protection characteristics.