onsemi has marked the CNY174SD as Obsolete.
5300Vrms isolation with a wide CTR window
The CNY174SD provides 5300Vrms of galvanic isolation, which is a standard rating for reinforced insulation in mains-connected industrial control, medical equipment, and power-supply feedback loops. This wide CTR spread means the designer must budget for the low end when calculating the LED drive current needed to guarantee a logic-level output at the receiver, and the high end when sizing the pull-up resistor to avoid saturation at the output transistor.
70V output, 50mA drive, and -55°C to 100°C range
The output transistor is rated for a maximum collector-emitter voltage of 70V and can sink up to 50mA continuous per channel. This voltage rating suits 24V and 48V industrial logic rails with margin, while the 50mA drive handles typical PLC input modules, relay coils, or DC solid-state relay gates without an external buffer.
6-SMD Gull Wing package, DC input, transistor output
Housed in a 6-pin SMD Gull Wing package, the CNY174SD is a surface-mount phototransistor optocoupler with a DC input and a transistor-with-base output. The base pin is brought out, allowing the designer to add a base-emitter resistor for improved noise immunity or to tailor the switching speed. The 1µs rise and 2µs fall times and 2µs turn-on / 3µs turn-off times place this part in the medium-speed class, suitable for 10-100 kbps data isolation or PWM feedback at switching frequencies up to a few tens of kilohertz.