STripFET II N-channel in a TO-220
The STP55NF06 is a 60 V, 50 A N-channel power MOSFET built on ST's STripFET™ II process. This is the kind of part you reach for when you need a general-purpose switching MOSFET for DC-DC converters, motor drives, battery management, or load switching in 12 V, 24 V, or 48 V systems — the 60 V drain-source rating gives enough headroom for a 48 V bus with transients.
Rds(on) and gate drive — the numbers that matter
If your gate drive is only 5 V, you will not hit that 18 mOhm figure; the Rds(on) will be significantly higher, and conduction losses will climb. For a 50 A continuous drain current, the 110 W power dissipation ceiling (at case temperature) means you must size the heatsink carefully — the TO-220 tab is the primary heat path, and the junction-to-case thermal resistance needs a proper thermal pad or grease and a mechanical clamp or screw.
Switching and input capacitance
The 60 nC gate charge is moderate — a standard gate driver with a 1 A to 2 A peak source/sink can switch it in a few hundred nanoseconds. The 1300 pF Ciss is low enough that the gate-drive loss is manageable even at switching frequencies in the tens of kilohertz. For hard-switched converters, the combination of 18 mOhm and 60 nC puts this part in the same class as other TO-220 N-channel MOSFETs in the 60 V / 50 A range — it is not a superjunction device, so do not expect the lowest Qg for a given Rds(on), but it is a solid workhorse for medium-frequency power stages.
If you need a second-source option, look at other TO-220 N-channel MOSFETs in the 60 V / 50 A / 18 mOhm class from Infineon, ON Semiconductor, or Vishay — but verify the pin-compatibility and gate-drive requirements, as the threshold and gate-charge specs vary.