That 920 mV forward drop at 20 A sets the conduction loss budget for a 150 V rail — in a 200 W output supply, each diode dissipates roughly 18.4 W at full load, so the TO-247-3 package and 175°C maximum junction temperature give the thermal designer room to manage that with a heatsink. The common-cathode pair shares the same cathode tab, which simplifies layout for center-tap secondary rectification or dual-output OR-ing where both anodes connect to separate windings or rails.
Package and mounting — TO-247-3 through-hole
Through-hole TO-247-3 with the metal tab as the common cathode. The tab is electrically live, so the heatsink must be isolated or the mounting hardware must use an insulating pad and shoulder washer. The three-lead form factor matches the standard TO-247 footprint used by many 150 V dual Schottkys — layout reuse across vendors is straightforward as long as the pin 1 assignment (anode 1, cathode common, anode 2) is verified against the existing PCB.
ST lists the STPS40150CW as Active product status. RoHS compliance is standard for ST's current TO-247 Schottky portfolio — no separate exemption certificate needed for EU markets.