What the 8 mOhm Rds(on) means on a 55 V, 80 A MOSFET
The Infineon BUZ111S is an N-channel SIPMOS power MOSFET in a TO-220-3 through-hole package. Vdss is 55 V. Continuous drain current is 80 A at 25 °C case temperature; the 300 W power dissipation limit (Tc) is the real thermal constraint.
Gate drive and switching — what the numbers tell you
Gate charge Qg is 185 nC at 10 V, and input capacitance Ciss is 4500 pF at 25 V drain-source. That is a moderate gate charge for a TO-220 device — a standard gate driver IC can switch it at tens of kHz without excessive drive current. The 4 V gate threshold (max at 240 µA) means it turns on cleanly with logic-level drive, but the 10 V drive voltage is needed to hit the minimum Rds(on). Operating temperature range is -55 °C to 175 °C junction — that is the full military-grade span, so this part is at home in engine bays, outdoor telecom cabinets, or downhole tools where the ambient is brutal. The TO-220-3 package (PG-TO220-3-1) is a standard through-hole footprint; it bolts to a heatsink with a single screw and the tab is the drain.
Lifecycle and compliance — active, but watch the RoHS flag
One catch: it is listed as RoHS non-compliant. If your assembly line or end-market requires RoHS exemption-free compliance, you will need to qualify an alternative or accept the lead-bearing finish. The TO-220-3 package and through-hole mounting make it a straightforward hand-solder or wave-solder part in a service or low-volume production environment.