50 ns trr — the switching-loss anchor
The STTH10LCD06CT is a 600 V, 5 A per diode fast-recovery rectifier in a common-cathode TO-220-3 package. Its 50 ns reverse recovery time (trr) is the parameter that defines its role: it is built for hard-switched topologies where recovery charge directly drives turn-off loss. In a continuous-conduction-mode PFC boost stage or a 400 V DC-link flyback clamp, that 50 ns trr keeps the switching node from ringing into the MOSFET body diode and holds the EMI signature within a reasonable budget. The 2 V forward drop at 5 A per die means 10 W conduction loss per diode at full rated current — the TO-220 tab must be heatsunk, and the common-cathode configuration means the tab is at the cathode potential, so a shared heatsink is fine as long as the system ground references it.
600 V blocking and 175°C junction — the voltage and thermal ceiling
The 600 V reverse voltage rating covers the 400 V DC-link bus with margin for transients. The 1 µA reverse leakage at 600 V is a room-temperature typical — expect it to rise with junction temperature, so the hot leakage should be budgeted in the bias supply design.