What the 75 ns trr means for your switching stage
The STTH4L06Q is a 600 V, 4 A fast recovery diode from STMicroelectronics, housed in a DO-15 axial package. Its 75 ns reverse recovery time (trr) places it squarely in the ultrafast class — clean for hard-switched PFC boost stages, secondary-side rectification in flyback converters, and motor drive snubbers where recovery losses matter. The 1.3 V forward drop at 3 A is typical for a 600 V planar structure; the 3 µA reverse leakage at rated voltage stays low enough for most off-line supplies. Junction temperature is rated to 175°C, the standard for industrial and automotive-grade silicon.
ST lists the STTH4L06Q as Obsolete.
DO-15 axial — through-hole mounting notes
The DO-204AC (DO-15) axial leaded package is a through-hole form factor. Lead forming for vertical or horizontal board mounting is standard; the body diameter and lead spacing are compatible with 0.6 mm diameter holes on a 5 mm pitch. The 4 A continuous rating assumes adequate copper pad area and airflow — derate for ambient above 25°C per the thermal resistance curve in the datasheet. No exposed pad; heat is conducted through the leads.