How to know TVS diode damage ?

[#1]

Hi !

How to know TVS diode damage ?
What kind tools to measure?

[AntonG]

Hi Jacky,

the simplest way to check if diode is damaged is to measure current through it at some fixed voltage below trigger voltage. Leakage current, if you like. Normally it should be nano-amp order of magnitude or lower. Refer to datasheet for exact values. Much higher current would indicate damage.

Since the idea is very simple you can use number of tools for measurement. In our automated measurement setups we use high-precision PSU to supply fixed voltage and measure current, but you can use curve tracer or any kind of voltage source and multimeter instead. However, if your tool doesn't have enough precision, you won't be able to detect very minimal damage.

Regards,
Anton

[Sergey_Karpov]

Dear Jacky!

There is even simpler way on how to check whether a TVS Diode is damaged or not. But before

going straight on to the Topic let us clarify the theoretical aspects about leakage current

of the pn-junction and afterwards define how to found when the device is damaged.

As my Colleague mentioned above a leakage current through TVS diode in the reverse

direction lies by some nano-amp. I would say it varies from device to devices. General

Purpose TVS oand Low-Cap TVS Diodes have different values of the leakage current from some

0.1nA up to 100nA - 1µA.

What does influence the amount of leakage current in a pn-junction?

A Doping Profile plays one of the significant role on it. When the Doping Profile of the

Diode is high, we have low breakdown voltage and but higher Capacitance value of the Diode.
Having a very high Doping Profile of the pn-junction causes the electron-hole pairs

recombinate faster in the Deplition Region in the pn-junction and increases the number of

these electron-hole pairs. This effect generates higher leakage current in the Diode.

Now let us go back to the question How to understand when the TVS Diode is damaged. Here in

Infineon we use the Transmission-Pulse-Line (TLP) method for TVS Diode characterization. We

stress diodes by some Voltage with a defined step and after every stress pulse the leakage

current is measured with a Source-Measure-Unit. Normally the leakage current must stay

constain with a slight fluctuation of some 1% of its previous value, which only is the

accuracy Problem of the SMU.

When the leakage current increases rapidly and grows up to 10x of its previous value we get

first degradtion of the TVS device. In this case the TVS Diode still shows the IV-Curve of

the Diode character but with a decreased breakdown voltage.
By applying further stresses the Diode is strongly degradated and burned out. That all

results that instead of IV-Diode Curve we get a IV Curve of the resitor smaller than 0.001

Ohm that is basically a short.

A Person who is not familiar with a measurement equipment can simply take a multimeter and

if the Diode was damaged you would measure a short between measurement tips.

Best regards,
Sergey