Is there any rule of the thumb at which power dissipated in an IC one should be able to feel that it is hotter than the other components?
More specifically, I have a "signal" that should consume nearly no power (<2mA @ 4.7V.) After identifying that the signal was always low, I removed the IC driving it, and supplied it with a lab supply. The track (with components attached to it) now behaves approximately like a resistor (resistance in the 10-30 ohms range) to ground.
I suppose one component is bad, and is leaking to ground (and therefore dissipating all this power.) At how much power dissipated in a single component should I be able to feel that it is hot with my finger?
Of course, there is no precise number (it depends on the exact component, the layout, the sensitivity of my finger, etc.)
Do you know at what power I'm sure to feel it, provided it's a "normal" IC?
EDIT: the components connected to the signal:
- CSD19538Q2T (x2)
- LED (APA2107LVBC/D) in series with a 2.2K resistor (0402 size)
- a 4.7V Zener to ground MM3Z4V7ST1G
- a 27k 0805 pull up resistor to 24V
Note that I cut the track going to the LT4294IDD#TRPBF as it was my main suspect at that time.
Also note that everything worked fine until a few days ago, so it's not a component placed wrongly.