100V 30A Schottky — the OR-ing and rectifier slot
The STPS30M100ST is a 100V, 30A Schottky barrier rectifier in a TO-220-3 through-hole package from STMicroelectronics. It is part of the STPS30 family of power Schottky diodes designed for low forward voltage drop and fast switching. Rated 100 V DC reverse maximum and 30 A average rectified current, this diode fits output OR-ing, freewheeling, and polarity-protection slots in 12V to 48V bus architectures where the 100V margin covers transients without avalanche stress.
Forward drop and leakage — the thermal budget
Forward voltage is 800 mV maximum at 30 A — the conduction loss at full load is 24 W, which sets the heatsink requirement. Reverse leakage is 175 µA at 100 V and 25°C junction. This doubles roughly every 10°C, so at 125°C junction the leakage approaches 28 mA — high enough to cause thermal runaway if the heatsink is undersized or the diode is paralleled without current-sharing resistors.
Through-hole TO-220 — heatsink and board integration
The TO-220-3 package (supplier device package TO-220) has a metal tab that is electrically common with the cathode. The tab must be isolated from the heatsink with a thermal pad or mica washer unless the heatsink itself is at cathode potential. Through-hole mounting means the diode stands off the board — the leads are formed for a 0.100-inch pitch pattern. The tab hole in the PCB should be plated through to the bottom-side copper pour for thermal transfer, and the leads should be soldered with a wave or selective-solder process.