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How to choose TVS tube?

Hardware design
September 07, 2020 by Isaias 1500

I want to do ESD protection for 5V voltage. How to choose TVS tube? What parameters should the datasheet look at.

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Jael Posted on September 7, 2020

1. The maximum clamping voltage VC of TVS should be less than the damage voltage of the protected circuit;

2. The reverse turn-off voltage VWM of the TVS must be greater than or equal to the maximum working voltage of the protected circuit. If the selected VWM is too low, the device may enter an avalanche, or the reverse leakage current may affect the normal operation of the circuit;  

3. AC voltage can only use two-way TVS;

4. Within the specified pulse duration, the peak pulse power Pm of the TVS must be greater than the possible peak pulse power of the protected circuit;

5. In high-speed lines, junction capacitance will affect the use of TVS-generally a TVS tube and a fast recovery diode are connected in reverse series (the junction capacitance of the fast recovery diode is small) to reduce the equivalent capacitance, which can meet the requirements of high frequency Use in the premises;

6. Need to consider derating (leave a margin) use.

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Seven Posted on September 7, 2020

1) Maximum operating voltage: It should be known that the TVS tube does not work when the circuit is operating normally, so the cut-off voltage of the TVS tube must be greater than the highest operating voltage of the protected circuit. But it should not be too high, otherwise the clamping voltage will be too high. Therefore, when selecting the highest voltage, comprehensive consideration should be given to the working voltage of the protected circuit and the withstand capability of the circuit.


2) TVS tube power selection: The rated transient power of TVS products should be greater than the maximum transient surge power that may appear in the circuit.


3) Clamping voltage: The clamping voltage of TVS should be less than the maximum transient safety voltage that the subsequent protected circuit can withstand.


4) Leakage current: In some low-power circuits or high-precision acquisition circuits, excessive leakage current may cause excessive circuit power consumption or excessive signal acquisition accuracy.

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Ieuan Posted on September 7, 2020

The energy of ESD is very small, generally by a special ESD protection diode, although it also belongs to the category of TVS tube, but compared with the TVS tube used for surge protection, its flow rate is very low, so it is generally small in size. The smallness also brings the benefit of its small junction capacitance, so it can be effectively used for ESD protection of some high-speed signal lines. As for the selection, please choose the type according to the ESD protection level you want to do, for example, you need to touch 8KV, when the air is hit to 15KV, the level of the selected ESD diode should also be at this level, and the reverse breakdown voltage should be selected at (1.3~1.6)*5V. At the same time, if it is used for high-speed signals, pay attention to the lower body capacitance. These few parameters will do.

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