Single-channel phototransistor optocoupler with AC/DC input
The FODM214R2 is a single-channel phototransistor optocoupler from onsemi's FODM214 series, rated for 3750Vrms isolation between input and output. The AC/DC input stage lets it sense both line-voltage zero-cross and DC logic levels without an external bridge — a feature that saves board space in appliance control or industrial I/O modules where the controller side must remain galvanically isolated from the field wiring. The output transistor can sink up to 50 mA continuous and block up to 80 V, which covers the 24 VDC and 48 VDC rails common in factory automation. The 3 µs typical rise and fall times are adequate for 10–100 kHz switching; for faster edges, the FODM217BR2V sibling offers a 2 µs rise time.
CTR spread and drive margin
The current transfer ratio spans 20% to 400% at a forward current of 1 mA. That 20:1 spread means the designer must check the minimum CTR at the actual LED drive current — if the MCU pin delivers only 0.5 mA, the output may not saturate fully. The typical forward voltage is 1.2 V, so a 3.3 V logic rail with a 330 Ω series resistor delivers about 6 mA, well within the 50 mA absolute maximum.
Active production and compliance status
ROHS3 compliant — no exemption-based conflict with EU or UKCA declarations.
Housed in a 4-SOIC (0.173", 4.40 mm width) surface-mount package, the 4-SOP footprint is a standard 1.27 mm pitch gull-wing — no fine-pitch challenges for a two-layer board.