1. TVS function

TVS ( Transient Voltage Suppres sor ) diode is a diode used to protect electronic devices from static electricity and unexpected surge voltages. The working principle is the same as the Zener diode, but it has ESD ( Electro   -   Static discharge ) features such as guaranteed endurance, high rated current, low junction capacitance, etc. specifically for protection.

Place TVS diodes in parallel with the electronic components you want to protect. When the circuit is working normally, the diode is in the OFF state; when a surge or other overvoltage is applied, it will turn into the ON state, and the pulse current is introduced to the ground through the TVS , clamping the overvoltage and protecting the back section of the circuit. As shown in Figure 1 below :

                                                        Figure 1    TVS diode protection function

2. TVS type: one-way and two-way

TVS diodes are divided into unidirectional and bidirectional types, and the TVS type to be placed must be selected based on the signal polarity. For lines with only positive polarity (or negative polarity) like DC power supply, or signals with only Low and High positive polarity like digital signals, both unidirectional and bidirectional types can be used. And if the signal has positive and negative poles, such as a non-biased analog signal or CAN (Controller Area Network) control area

For network communication, please use the bidirectional type.

3. Examples of TVS communication interface usage solutions

The figure below is an example of configuring TVS on various communication lines . Since TVS has parasitic capacitance between terminals, if the capacitance is large, it will affect the signal waveform and the communication quality will be degraded. Therefore, components must be selected whose capacitance value is suitable for the frequency of the communication line.

1 ) CAN interface electrostatic protection solution

2 ) USB3.0/TYPE-C electrostatic filter protection solution

3 ) Vehicle Ethernet protection solution

4) RS485 surge filter protection solution

Shanghai Leiditech Electronics specializes in providing customers with electromagnetic compatibility EMC design services and provides free laboratory testing.