100 V, 20 A — the conduction-loss floor in a full-pack tab
The FERD20H100SFP is a 100 V, 20 A Field Effect Rectifier Diode from STMicroelectronics, built in the FERD (Field Effect Rectifier Diode) family that trades a slightly higher forward drop than a Schottky for a much lower reverse leakage at temperature. At 20 A the forward voltage is 705 mV max — the conduction loss at full load is about 14 W, which the TO-220FPAB full-pack package must sink through the tab to the heatsink. The 100 V reverse rating gives a solid 1.25× derating margin on a 80 V bus; the 175°C junction ceiling allows the die to run hot in a confined enclosure as long as the thermal path is managed.
Reverse leakage — 140 µA at 100 V, the hidden thermal driver
Reverse leakage is specified at 140 µA at 100 V junction temperature. In a FERD the leakage rises with junction temperature more slowly than in a Schottky, but it still doubles every 10–15°C above 100°C. At the 175°C max junction the leakage current can dominate the self-heating budget, so the heatsink design must keep the tab temperature below about 120°C to stay in the efficient region of the leakage curve.
TO-220FPAB — full-pack isolation, no insulating washer
The TO-220FPAB full-pack moulding encapsulates the die and isolates the metal tab — the tab is at circuit potential, not the cathode. This eliminates the need for a silicone-insulator pad and a shoulder washer on the mounting screw. The through-hole leads fit a 0.100-inch pitch footprint; the tab hole is sized for an M3 screw. The thermal resistance junction-to-case is lower than a standard TO-220 with an insulator, but the full-pack body is thicker, so the heatsink must be drilled to clear the plastic stand-offs on the back face.