I am using an OnSemi NTGD3148N dual MOSFET in a project. I cannot find a specification anywhere in the datasheet stating the isolation between the devices; and this holds true for most dual MOSFETs for example Si4946EY (which I used in a different project.)
Obviously I can't put 100kV on one drain pin and 0V on another without something blowing up. (Ignoring for the moment that it can't take 100kV D-S; the source in this example is left floating.)
This is important for me, as I am switching two independent loads which cannot be allowed to short together. E.g. one might be 12V and another 5V.
Best Answer
If isolation isn't specified in the datasheet then I wouldn't assume it's there. Most likely both FETs are on the same substrate. That means they are sortof dual diode isolated, but the breakdown voltages of those diodes probably isn't much more than the max D-S voltage allowed.
In any case, that's just guessing on my part. If it's not in the datasheet, then its not in the device for practical purposes.