4170 Vrms isolation with transistor output
The onsemi CNY174SM is a single-channel optoisolator with a DC input LED and a phototransistor output that includes a base connection. The 4170 Vrms isolation rating means the primary-to-secondary barrier withstands this test voltage for one minute per UL 1577 — a figure that supports reinforced isolation in mains-referenced circuits where the working voltage stays below 250 Vrms. Current transfer ratio (CTR) is specified at 160% minimum and 320% maximum, both at 10 mA forward current — a tight enough window to guarantee logic-level output swing across the full load range without overdriving the LED.
Switching speed and output drive
Rise and fall times are 4 µs and 3.5 µs respectively (max), with turn-on at 2 µs and turn-off at 3 µs typical — fast enough for 100 kHz data rates in isolated feedback loops or PLC digital input modules where the PLC scan rate is the bottleneck, not the isolator. The output transistor handles up to 70 V collector-emitter and 50 mA continuous current, with Vce(sat) capped at 400 mV — adequate for driving a 5 V logic input or a small relay coil through a series resistor.
Package, temperature, and compliance
Housed in a 6-SMD gull-wing package (supplier device package 6-SMD), the CNY174SM is surface-mount ready for reflow assembly. Operating temperature spans -40°C to 100°C, covering industrial and outdoor telecom enclosures. The part is available to order against an RFQ through independent distribution channels.