4170Vrms isolation and CTR binning
The CNY17F3M is an onsemi single-channel optoisolator with a DC input and a phototransistor output, rated for 4170Vrms of galvanic isolation. That isolation voltage defines the safety barrier between the low-voltage control side and the high-voltage power side — typical for motor drives, power supplies, and PLC I/O modules where transient overvoltage separation is required. The current transfer ratio is binned at 100% minimum and 200% maximum at a forward current of 10 mA. This means the LED drive circuit can count on at least 10 mA of collector current from 10 mA of input current, with a ceiling that prevents the output from saturating too hard in high-gain designs. The narrow 2:1 CTR spread reduces the worst-case variation compared to wider-bin parts, simplifying the resistor selection on the input side.
Switching speed and output limits
Turn-on and turn-off times are typically 2 µs and 3 µs respectively, with rise and fall times of 4 µs and 3.5 µs maximum. These numbers suit 10–100 kHz switching applications such as isolated gate drives or feedback loops in offline power converters where the propagation delay must be under one switching cycle. The output transistor is rated for 70 V collector-emitter and can sink up to 50 mA continuously, with a Vce(sat) of 400 mV maximum.
Temperature range and application envelope
The operating temperature range spans -40°C to 100°C, covering industrial and outdoor telecom environments. Below -40°C the LED efficiency degrades; above 100°C the phototransistor dark current rises and CTR drifts downward — the 100°C ceiling is the practical limit for continuous operation in a sealed enclosure.