How to protect MPQ4423H against Burst and Surge at VIN=30V?

We want to use MPQ4423H (like in Evalboard EV4423H).
VINmin=10V and VINmax=30V.
A TVS-diode (SMCJ28CA) does not protect the chip beacuse of the high clamping voltage (45V).
Do you have any idea to solve this topic without changing the chip type?

How much surge? Is this an automotive application? As I recall LT spice has some canned automotive transients that you can test you input side with, No need to have the buck implemented, you just want to see what the surge combined with your input emi filter, surge suppression diode and filter cap do.

1kV 2Ohm at DCIN. No, this is not an automotive application. Thank you for your suggestion about LTspice. I will try it, but this does not solve my problem.

So 500A of short circuit current and can raise the 30V to 40V before trouble. The zener would need a dynamic impedance of 10/500 20mohm. Tough. Is this an 8X20usec pulse? I swag that a perfect 750uF cap would soak up the pulse. ESR will be an issue. I would be fooling with an input L with some resistance and a big C plus the clamp diode. Luckily your application doesn’t have to be cheap or small.

I would guess that what you want is an MOV direct on the input these are way more rugged than a TVS as the energy is dissipated in the bulk of the material rather than just a a junction.

It won’t be enough a 20mm MOV is going to clamp the pulse down to 150V or so, but then you use the input EMI filter and a TVS on to finish the job.

Thank you for your suggestions. You are right with MOV, Inductor, TVS and a cap. But the TVS is clamping above the absolute maximum rating of the buck regulator, as I wrote in my first post.

Bigger cap ( or lower ESR) bigger inductor ( or higher R) bigger TVS ( or double up)