Question
What is Analog Devices recommended application circuit to prevent a ADuM2250isolator fault causing the device from overheating and damaging the isolationbarrier ?
Answer
This is an interesting question, and it depends on what your system expectsfrom our device.
What are the potential overvoltages/transients in your system?
What standard are you conforming to? IEC60601? The ADuM2250 and ADuM2251 arecertified to IEC 60601-1. The RI package with guaranteed 8mm creepage providesthe highest approved working voltage.
The fault condition that will affect our part is if the voltage rises above theabsolute max. In that case the ADuM2250 can go into latch-up. This willdissipate a lot of power on our device if there is an unrestricted supply.With enough power something will melt. If you expect the part to retainfunctionality, then the goal is to keep the power dissipation such that thejunction temperature stays below 150C. If power is reset the part should comeback.If your goal is only to retain safety isolation, then the temperature of thedie will have to rise above the decomposition temperature of the polyimideinsulation, which is conservatively 300C.You can figure out the power dissipation based allowed based on the Theta JA ofthe package, and figure the power allowed for each case above. Compare that tothe available power from the supply. If you need additional limiting, you canadd resistance to the VDD and data I/O lines.