170 V, 20 A dual Schottky — what it handles
The STPS40170CG-TR is a dual Schottky rectifier from STMicroelectronics, configured as a common-cathode pair in a single D2PAK (TO-263AB) surface-mount package. Each diode is rated for 170 V reverse voltage and 20 A average rectified current, giving a total of 40 A in a compact footprint. The 920 mV forward drop at 20 A is typical for a 170 V Schottky — the trade-off for the high blocking voltage is a higher Vf than low-voltage Schottky types.
Rated for a maximum junction temperature of 175°C, this diode can tolerate sustained high-temperature operation in cramped enclosures or under overload conditions. The D2PAK's exposed tab conducts heat to the PCB copper plane — the thermal pad area under the tab sets the effective RthJA. Derate the 20 A per diode above 100°C case temperature per the datasheet curve.
Reverse leakage at 170 V
At 170 V reverse bias, the leakage current is 30 µA typical. This is low enough for most power supplies and OR-ing circuits, but note that Schottky leakage doubles with every 10–15°C rise in junction temperature — at 125°C the leakage will be significantly higher, so account for it in the standby power budget.