Schottky pair for 80 V rail rectification
The STPS40SM80CT is a dual Schottky rectifier from STMicroelectronics, pairing two 20 A diodes in a common-cathode configuration inside a single TO-220-3 through-hole package. It is rated for an 80 V maximum reverse voltage and delivers a forward voltage drop of 800 mV at 20 A per diode, with a fast recovery time of ≤500 ns above 200 mA.
20 A per leg — thermal budget in the TO-220 tab
Each diode in the pair handles 20 A average rectified current. At that current the forward drop is 800 mV, so each leg dissipates 16 W when conducting. The TO-220 package relies on the metal tab for heatsinking — without a proper heatsink the junction temperature will climb toward the 175 °C maximum, and the reverse leakage at 80 V (50 µA typical) rises sharply with temperature. A heatsink with a thermal resistance below 3 °C/W keeps the junction within a safe operating margin in continuous duty.