55 V N-channel HEXFET — the conduction-loss story
The IRFZ46ZSTRLPBF is an Infineon HEXFET® N-channel power MOSFET rated for 55 V drain-source and 51 A continuous switching current. That 55 V rating gives comfortable margin on a 48 V nominal bus (typically 54 V max under float) and plenty of headroom for a 24 V system where you want the lowest Rds(on) available in the voltage class.
Rds(on) and gate drive — what the numbers mean at the bench
The 13.6 mOhm Rds(on) is specified at Vgs = 10 V, which is the standard gate-drive voltage for a 12 V rail or a bootstrap supply. If your gate driver only delivers 5 V, the on-resistance will be higher — the datasheet's typical curve shows the Rds(on) roughly doubles below 6 Vgs. The 46 nC total gate charge at 10 V means a gate driver sourcing 1 A can switch the FET in about 46 ns; at 100 kHz switching frequency, the gate drive power is roughly Qg × Vgs × fsw = 46 nC × 10 V × 100 kHz = 46 mW, well within a typical driver's budget. The ±20 V maximum gate-source rating gives headroom for gate-drive overshoot in hard-switching topologies — a 12 V gate drive with 5 V of ringing stays inside the window. The 4 V threshold at 250 µA is a typical logic-level threshold; the FET turns on hard above 6 Vgs.
Package, temperature, and board integration
Surface-mount package — the specific case style is a D2PAK (TO-263) compatible footprint. The 82 W power dissipation assumes an infinite heatsink on a 25 °C ambient; real-world dissipation depends on the PCB copper area under the drain tab. Derate power above 25 °C per the thermal resistance in the datasheet.