3.7 mOhm Rds(on) — the conduction loss floor
The IRF7862TRPBF: The headline spec is the 3.7 mOhm maximum on-resistance at Vgs=10 V and Id=20 A — this sets the conduction loss floor in a synchronous buck converter or load switch. At 20 A, the I²R loss is under 1.5 W, but the 8-SOIC package dissipates only 2.5 W max at 25 °C ambient, so the board copper and airflow must carry the thermal budget.
Gate drive and switching — 45 nC at 4.5 V
Gate charge is specified at 45 nC max with Vgs=4.5 V, meaning the MOSFET can be driven from a 5 V logic rail with moderate gate-driver current. The input capacitance Ciss is 4090 pF at Vds=15 V — the driver must supply the Qg total at the target switching frequency. For a 100 kHz buck, the average gate current is 45 nC × 100 kHz = 4.5 mA, well within a standard driver's capability.
30 V Vdss — voltage headroom check
The 30 V drain-source rating gives 50 % headroom on a 12 V rail and 25 % on a 24 V rail. For 24 V systems with inductive loads or hot-plug transients, the margin is tight — a 36 V or 40 V rated part is safer if the bus sees spikes above 30 V. The gate-source maximum is ±20 V, so a Zener clamp on the gate is unnecessary for logic-level drive.
Thermal and package — 2.5 W in an 8-SOIC
The 8-SOIC (8-SO) surface-mount package limits power dissipation to 2.5 W at 25 °C ambient. At 21 A continuous drain, the on-resistance at 150 °C junction (the max operating temperature) rises to roughly 1.5× the 25 °C value — about 5.6 mOhm — pushing I²R loss to 2.5 W. The board layout must provide a low-thermal-resistance path through the copper pour and vias to keep the junction below 150 °C.
Lifecycle and sourcing
It is ROHS3 compliant.