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Transient voltage suppressor devices

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Transient voltage suppressor devices

The working principle of a TVS is the following: Once the voltage at TVS node exceeds the

breakdown voltage VBR, the TVS will clamp the voltage across it, reaching a clamping level

VCL that depends on the current flowing through the TVS

Two kinds of TVS can be used: unidirectional or bidirectional.

Unidirectional

A unidirectional TVS clamps the voltage differently depending on the direction (V > 0 or

V< 0).

For V > 0, it will act as a diode in forward conduction, with a clamping voltage below 1 V,

generally around 0.7 V.

surge tries to force it lower.

Figure 2. Unidirectional TVS behavior

Bidirectional

A bidirectional TVS clamps the voltage in the same way whatever the direction (V > 0 or

V< 0).

The voltage will be able to vary from -VBR to +VBR but will be clamped to –VCL or VCL if a

surge tries to push voltage out of boundaries.

Figure 3. Bidirectional TVS behavior

I current

V voltage

VBR

VCL

I

V

VF

I current

V voltage

VBR VCL

VBR

VCL

V

I