What makes this optocoupler different — AC/DC input on a single channel
The HCPL3700SDV accepts both AC and DC inputs and converts them to a logic-level output through a Darlington stage, which means a single part can monitor a 50/60 Hz mains line or a 24 VDC control signal without external rectification or level shifting. Rated for 2500 Vrms isolation across an industrial temperature range of -40 to 85 °C, it fits applications where galvanic isolation between a high-voltage AC line and a low-voltage logic input is required — think PLC digital inputs, motor drive status feedback, or power supply monitoring.
Switching speed and output drive — what the numbers mean for your BOM
Turn-on time is 6 µs typical, turn-off 25 µs typical, with a 45 µs rise and 0.5 µs fall time. The 25 µs turn-off means the output stays high for roughly one cycle of a 50 Hz line after the input drops — fast enough for over-voltage detection but not for cycle-by-cycle current zero-crossing.
Obsolete — sourcing reality for this optocoupler
onsemi has marked the HCPL3700SDV as obsolete. Available through independent distribution channels — quantities are lot-specific and confirmed at RFQ. The 8-SMD Gull Wing package and Tape & Reel format mean the part is compatible with standard pick-and-place assembly, but any replacement will require a board-level qualification.