Schottky pair in a TO-220 — what the ratings tell you
The STPS640CT is a dual Schottky rectifier in a common-cathode configuration, rated 40 V reverse voltage and 3 A average forward current per diode.
630 mV forward drop — the thermal budget driver
At 3 A per diode, the forward voltage is 630 mV maximum — that's about 1.9 W per diode at full load. In a TO-220 package with a heatsink tab, the junction temperature stays under the 150°C maximum if the thermal path is managed. The 100 µA reverse leakage at 40 V is typical for a 40 V Schottky; leakage rises with temperature, so the thermal design should account for it at elevated junction temperatures.
Obsolete — plan your BOM around surplus sourcing
STMicroelectronics lists the STPS640CT as obsolete. No official successor is recorded in the lifecycle entry. If you are stocking spares or supporting a legacy board, this is a last-time-buy candidate; once the surplus channel dries up, the only option is a pin-compatible substitute from the same Schottky family.
Through-hole TO-220 — board-fit checklist
The TO-220-3 package with through-hole leads mates into a standard 0.100-inch pitch footprint. The common-cathode pair shares the centre tab, so the PCB layout must connect the tab to the output rail and route the two anodes to separate input phases or windings. The tube shipment means the parts arrive in anti-static tubes; store them in the tube until placement to avoid lead damage.