Overcurrent vs Overthermal

[dknguyen]

It's pretty obvious about the difference between overcurrent and overthermal protection, but why are they both needed (in some cases). Isn't the whole point to keep the unit from overheating? If so for a power application (like motor drive), from the perspective of protecting the device (not powering monitoring or anything else), who cares how much current is being pulled unless it overheats the unit? Can't this be done with just overthermal protection?

 

[bioborg]

i'm no expert yet, but I imagine there is overcurrent protection because the current coming in a surging manner will cause a reaction alot faster than overheating. It takes time for a unit to heat up, at least more time than it takes current to cause damage. Time would be the reason, I think.

 

[Roff]

Yeah, I believe excessive current can cause localized destructive hot spots. Due to the thermal time constant of the die and package, the thermal sensor will not detect these hot spots rapidly enough to avoid damage.