# Determining the surge duration of a double exponential transient?

I am trying to calculate the maximum single peak pulse power rating of a thick film resistor that will be subjected to a significant amount of inrush current upon each power up.

The datasheet has a nice plot of maximum power vs surge duration for each package size on page 2, but I am struggling to determine the appropriate way to determine the surge duration of my transient.

The transient has somewhat of a double exponential shape, what interval would typically be considered the pulse/surge duration of a waveform like this?

My particular transient has the following timing characteristics:

• t_1 = ~5 ms (rise time to peak value, 0%-100%)
• t_2 = ~15 ms (cumulitive time to reach the 50% decay point)
• t_3 = ~95 ms (total time until transient is effectively 0 again)

I feel like I remember learning that you measure out to the point at which the amplitude has decreased back down to 50% of the maximum, so in my case, 15 ms, but I can't find any sources online that back that up.