A 1.9 mOhm switch for 60 V rails — sizing the loss budget
185 A continuous — what the package and temperature grade allow
The continuous drain current is rated 185 A when the case temperature is held at 25°C, and 33 A when the ambient air is 25°C with no heatsink. That gap is the thermal reality: the TO-220-3 package (PG-TO220-3-U05) can pass the current if the junction stays under 175°C, but the 3.8 W ambient dissipation limit means you need a heatsink for any load above a few amps.
Gate drive and input capacitance — what the 6 V / 10 V spec means
The drive voltage range is specified as 6 V minimum for the lowest Rds(on) and 10 V for the rated maximum performance. At 10 V the 1.9 mOhm figure is guaranteed; if your gate drive rail is 5 V or 3.3 V, the on-resistance will be higher — check the typical curves in the datasheet. The 7300 pF input capacitance at 30 V drain bias is moderate for a 60 V device of this current class; it loads the gate driver with about 162 nC per switching event, so a driver capable of sourcing at least 2 A peak is a safe starting point for keeping switching times under 100 ns.