I need to protect the schematic from the surge transient voltage 1.0 kV 1.2/50 us (standard surge model).
To accomplish this I planned to use two SMBJ200CA TVSs in series at the input and make all following circuit withstanding up to 800V voltage:
I have a filing that this schematic will work fine. However TVS's will work in the unspecified area. Let me explain:
In the datasheet specified that the clamping voltage (Vc) of this part is 324V and the current at this point (Ipp) should be 1.9A:
If I'd look further in the datasheet I will see the voltage-to-current chart ending with Vc/Ipp point:
I checked out Littlefuse, Bourns and SMC Diode Solutions datasheets for the information regarding how it will behave beyond this point - no information :(
I think that 1.9 Amps is definitely not enough for protection. I estimated that the current in the worst case scenario should be up to 500 Amps - 250 times more than specified and I have no source for estimation.
The only thing I can do - put the real device(s) to the test until destruction and made some estimation upon these tests. But I don't like to use any device under unspecified condition as I can not be sure for these specs.
I'd spell the questions in the following way:
- Do you share my opinion that this schematic will work fine in real world?
- Is TVS a right device for this purpose? Or should I add anything extra to the schematic to make it more reliable (or move working points to the specified area)? I don't like varistors as they are big, expensive and fire-able.
- Please share any of your thoughts on the subject...