Recovery speed and what it means for the circuit
The 1N645UR-1 is a standard recovery diode with a recovery time greater than 500 ns at forward currents above 200 mA. This places it in the slow-switching class — the reverse recovery transient lasts long enough to cause shoot-through losses in a 100 kHz+ switching supply, so it belongs in line-frequency rectification, snubber, or DC bus isolation stages where the recovery tail does not limit efficiency.
225 V reverse standoff and 400 mA forward rating
Rated 225 V DC reverse maximum and 400 mA average rectified forward current. Reverse leakage is 50 nA at the 225 V rating, which keeps the off-state power loss below 12 µW in a high-impedance bias circuit.
Junction operating range is -65 °C to +175 °C — the full military temperature band. The DO-213AA (MELF-style) surface mount package has no leads to fatigue under thermal cycling, which suits the -55 °C cold-soak to +125 °C hot-run profile in avionics or downhole instrumentation. The package is rated for standard reflow profiles; the metallized end caps handle the solder joint, not the glass body.