What this optoisolator does on your board
The FODM217A is a single-channel phototransistor optoisolator from onsemi's FODM217 series, delivering 3750Vrms galvanic isolation between a DC input and a transistor output in a 4-SOP surface-mount package. With a current transfer ratio (CTR) specified at 80% minimum and 160% maximum when the forward diode is driven at 5 mA, the part provides enough gain headroom to drive logic inputs or low-power loads without an external buffer — but the 80% floor at 5 mA is the number to design to for worst-case margin.
Switching speed and temperature range
Typical turn-on and turn-off times are 3 µs each, with rise and fall times of 2 µs and 3 µs respectively — fast enough for 100 kHz isolated communication or PWM feedback, but not for high-speed digital isolation above 1 Mbps.
Package and mounting details
The 4-SOP footprint is compatible with standard SOIC-4 land patterns; no special pad geometry is required beyond the datasheet recommendation.
The device is ROHS3 compliant, meeting the latest EU restriction-of-hazardous-substances directive without exemption.