Photodarlington optoisolator for high-gain isolation
The FODM352 is a single-channel photodarlington optoisolator from onsemi. Its Darlington output stage delivers a minimum current transfer ratio of 1000% at just 1 mA LED drive, meaning the output can switch loads up to 150 mA continuous while the input side draws minimal current — ideal for 3.3V or 5V logic interfaces where drive current is tight. Reinforced isolation of 3750Vrms separates the input and output, meeting safety requirements for industrial controls, motor drives, and power supplies where galvanic isolation is mandatory.
Parametric deep-dive: gain, drive, and timing
With a CTR minimum of 1000% at If=1 mA, the FODM352 can be driven by a GPIO pin sourcing less than 2 mA while the output side switches a 150 mA load. The output transistor saturates at 1.2 V max (Vce) at the rated output current, keeping power dissipation in the opto low even when driving a 24 V industrial load. Rise and fall times are 20 µs and 100 µs typical — adequate for DC switching and low-frequency signal isolation below 5 kHz.
No end-of-life notification or successor has been issued.