LT4356 along with SMPS filtering


We are developing a product that has a boost converter, but also needs to be able to survive outside the boost converters recommended operating range. To do this I was going to use the LT4356. 

Obviously to condition the input I was going to do the following:

-Add a bidirectional TVS diode

-Add a reverse protection diode

-Add a damped L C filter in order to eliminate conducted emissions

-Used a surge stopper device to protect the input of the boost

I suppose my question is: Is it better to place the surge stopper before or after the LC filter?

If the surge stopper sits between the input and ground I'm concerned it will be affected by the input ripple of the boost convert that comes after it. Although if it comes after the LC filter it will have any input transients filtered.

I think the boost input may have up to 300mV of voltage ripple, but (hopefully) with out a tone of harmonic content, since the switching is done on the other side of the boost inductor  



Steve H

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