What the 45 ns trr means for a 100 kHz PFC stage
The STTH20R04G-TR is a 400 V, 20 A fast recovery diode in a D2PAK (TO-263AB) surface-mount package. Its 45 ns reverse recovery time places it in the standard fast-recovery class, making it a candidate for continuous-current-mode (CCM) boost PFC stages where the diode's stored charge must clear before the next switching cycle begins.
Forward voltage and junction temperature — the thermal budget
Maximum forward voltage is 1.7 V at 20 A — the conduction loss at full rated current is 34 W, which must be sunk through the D2PAK's exposed pad. The 175°C maximum junction temperature provides margin above the typical 150°C ceiling of standard rectifiers, but the thermal resistance from junction to case (RθJC) in the datasheet's absolute-max table is the number to budget against the heatsink or PCB copper area. Reverse leakage at 400 V is 20 µA — negligible in the on-state but a contributor to off-state losses at high ambient temperatures where leakage doubles every 10°C above 25°C.
Package and board fit
The D2PAK (TO-263AB) footprint is the surface-mount equivalent of the through-hole TO-220.