I can't see any reason for the 100 Ohm resistor, how about ommiting it?

Hallo Mahmood,

if input voltage rises up to no more than 660V, then you can omit it. But use of 100R resistor has some advantage, when extreme overvoltages or heavy ESD events can occur. Think also about lightnings.
But I agree with you, most developers would omit it, I think.

Kai