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TVS Diodes power ratings for IEC 61000-4-5

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MEHRANPOUR

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Hi,
I want to put a TVS diode between positive and GND lines (Earth and GND are the same in my board) on my board to pass the surge test (IEC 61000-4-5).
When you check datasheets of TVS diodes they are mostly mentioned the IEC standards that they support, but my problem is I don't know which package(SMA, SMB, SMC) is suitable for my case.
If I want to pass the category 4 in surge test which is 4kV Do I need SMC (500W)package ? or SMA package (400W) is enough?
How can I do the calculation from a TVS diode datasheet to comply with the standard?
My board is a 48V DC Drive
 

Hi,

You may calculate the pulse energy that has to be dissipated by the diode.
Or you run a simulation doing the math for you.

Klaus
 

You should clarify which of the 61000-4-5 test pulses has to be handled by the protection circuit, also what's the intended TVS voltage. TVS ratings are referring to 10/1000 us pulses which have relative low current. Level 4 1.2/50 us test pulse has 2 kA peak current and exceeds the ratings of the mentioned diodes.

Another point is that sufficient TVS diode rating doesn't guarantee that your circuit survives the TVS clamp voltage.
 

According to my reading of the standard, power lines have to be tested with 1.2/50 µs (8/20 µs short circuit) pulses. You should choose TVS diodes that are specified for 8/20 µs, e.g. Littelfuse LTKAK3 series.
 

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