Isolation and signal transfer
The CNY17F1SR2M is a single-channel transistor-output optocoupler from onsemi, offering 4170 Vrms galvanic isolation between the DC input and the transistor output. This isolation rating suits it for breaking ground loops and protecting low-voltage logic from high-side transients in industrial control, power supply feedback, and PLC digital input interfaces.
Current transfer ratio and switching
The current transfer ratio (CTR) is specified at 40% minimum and 80% maximum, both measured at a forward current of 10 mA. This 2:1 CTR range means the output transistor can saturate reliably across the full operating temperature band without overdriving the LED — the designer sizes the pull-up resistor for the minimum CTR to guarantee logic-level swing at the receiver. Switching speed is characterised by a 2 µs turn-on and 3 µs turn-off time typical, with rise and fall times of 4 µs and 3.5 µs maximum respectively. These numbers place the part in the medium-speed class — adequate for 100 kHz isolated data links or PWM feedback loops, but not for high-speed digital isolation above 1 Mbps.
Output ratings and temperature range
The output transistor is rated for 70 V maximum collector-emitter voltage and 50 mA continuous output current per channel. This voltage headroom covers 48 V industrial rails with margin, and the 50 mA current drives small relays, logic inputs, or LED indicators directly without a buffer transistor.
The gull-wing leads provide a visual solder-joint inspection point and moderate standoff for cleaning under the body.