What is the reference for High side IC with internal mosfet driver
Some of the circuitry is referenced to the source of the power MOSFET. In this particular case there may be nothing referenced to ground but usually there is (control input for high side driver, for example). There needs to be level translation between the two. 

You can see this if you read the datasheet for the LTYswitch:


For a high side bootstrap driver you can see the level translation circuitry as in the below diagram extracted from the datasheet for the IRS2110:



Neither one of these datasheets is all that clear on where the references are for the high side drivers etc., unfortunately.