TPS26601 Industrial eFUSE Circuit Design
If the datasheet shows a pullup, it's probably adequate unless you're in a high noise or high EMI environment. 
Sometimes you want a reference ground that has very little current flowing; the potential of your power ground might vary based on instantaneous current. 
If your MCU and chip are using the same ground and the voltages are compatible, it should work without an optocoupler.  Just make sure you don't violate the input voltage range.