Saw a calculation of stress in a datasheet (page14) here - http://tinyurl.com/43465sv [Broken] (The device drives a Mosfet.) How do you relate the P^2 t stress calculation in the datasheet to the Safe operating area curve in a Mosfet datasheet. If the Stress is 20W^2 sec, then how do you interpret it? The Mosfet should be able to withstand 20watts for 1sec. The watt square is confusing me. Why watt square*t? why not joules.