4170 Vrms isolation for safety-barrier designs
The CNY17F4SM from onsemi is a single-channel optocoupler built for applications that need a reinforced isolation barrier — 4170 Vrms between input and output. That rating suits it for industrial motor drives, PLC digital inputs, and medical patient-monitoring interfaces where a fault on the high-voltage side must not reach the low-voltage control logic.
CTR range sets the LED drive budget
The current transfer ratio is specified at 160% minimum to 320% maximum, measured at If = 10 mA. Output transistor can handle up to 70 V collector-emitter and 50 mA continuous current. The 400 mV Vce(sat) maximum keeps the voltage drop low when driving a downstream logic input.
Switching speed for 10–100 kHz isolation links
Typical turn-on time is 2 µs, turn-off time 3 µs, with rise and fall times of 4 µs and 3.5 µs respectively. That puts the usable data rate around 100 kHz — fine for status feedback, relay drivers, and low-speed serial isolation, but not for high-speed comms like CAN or Ethernet. The 1.35 V typical forward voltage at 10 mA LED current is standard for an infrared LED; the 60 mA absolute-maximum forward current gives headroom for transient overdrive.