What this optoisolator is and where it fits
The FOD814AS is a 1-channel optoisolator from onsemi with a transistor output and a 5000Vrms isolation rating. It accepts both AC and DC input, which means a single part can handle line-voltage zero-cross detection or a logic-level signal from a microcontroller. The 4-SMD Gull Wing package suits surface-mount assembly, and the operating temperature range of -55°C to 105°C covers industrial and outdoor equipment where the PCB sees thermal cycling.
Key ratings and what they mean for your BOM
The 5000Vrms isolation voltage is the headline spec for safety-rated designs — it meets the reinforced insulation requirement in many industrial and medical power supplies without needing a second opto in series. Current transfer ratio (CTR) is specified at 50% to 150% at 1 mA forward current. That range tells you the output transistor can sink enough current to drive a logic gate or a low-power relay directly, but you should design the pull-up resistor for the minimum CTR to guarantee switching at low input current. The transistor output is rated for 70 V and 50 mA continuous. That is enough for 24 V PLC inputs, 5 V logic level shifting, or driving a small DC load, but not for a power relay coil without a buffer transistor. Rise and fall times are 4 µs and 3 µs typical. That limits the switching frequency to about 100 kHz for clean edges — fine for 50/60 Hz line sensing or low-speed data isolation, but not for high-speed serial buses.
Lifecycle and sourcing reality
The FOD814AS is listed as Active and ROHS3 compliant. The 4-SMD Gull Wing package is a standard footprint shared with many optoisolators, so the reel can be stored in a dry cabinet with the rest of the SMD inventory. No stock-holding claim — sourced per RFQ.