SCR-output optocoupler for AC load switching
The Toshiba TLP748J(F) is a single-channel SCR-output optocoupler in a 6-DIP through-hole package. It provides 4000 Vrms isolation between the LED input and the SCR output, with a 600 V off-state voltage rating and 150 mA RMS on-state current capacity. The 15 µs turn-on time suits line-frequency AC switching applications like solid-state relays, motor contactors, and triac drivers where the output SCR commutates at the zero-crossing of the mains waveform.
600 V off-state and 4000 Vrms isolation — what they mean on the BOM
The 600 V off-state rating means the SCR can block peak repetitive voltages up to that level, which covers 240 VAC mains with margin for transients. The 4000 Vrms isolation is the reinforced-insulation barrier between the low-voltage control side and the high-voltage load side — sufficient for safety isolation in industrial equipment that must meet IEC 60950 or similar standards. The 15 µs turn-on time is fast enough for 50/60 Hz phase-control firing; the non-zero-crossing output means the SCR triggers immediately when the LED current exceeds the 10 mA Ift threshold, so the designer must handle turn-on timing in the drive circuit rather than relying on internal zero-cross circuitry.
The approvals from BSI, SEMKO, and UR cover European and North American safety certification for the isolation barrier — a useful check for export builds.
Package and mounting — through-hole 6-DIP
The 6-DIP package with 0.400-inch (10.16 mm) pin spacing is a standard through-hole footprint. The through-hole mounting suits designs where wave soldering is preferred over reflow, or where the optocoupler sits on a separate high-voltage PCB alongside relays and terminal blocks. The supplier device package is 6-DIP.