TVS diode dissipation help
As it says right in the datasheet, it can withstand 6.5W dissipation on an infinite heatsink. An unheatsinked chip will increase 75C per watt, limiting it to 2W before it reaches its maximum operating temperature. The point of a heatsink is to reduce its junction thermal resistance to some value less than 75 so that it can dissipate more power without hitting 150C. The 6.5W figure is saying that even if you kept it cold, that's the limit for the internal workings of the chip.