onsemi has marked the CNY171SD as Obsolete.
5300 Vrms isolation — the fit for reinforced safety barriers
The CNY171SD provides 5300 Vrms galvanic isolation between input and output. That rating qualifies it for reinforced insulation in mains-connected circuits — think AC-DC power supplies, motor drive feedback paths, or any interface where the low-voltage control side must be protected from a high-voltage bus. The 1 µs rise and 2 µs fall times are fast enough for 100 kHz switching signals but not for high-speed data links; this is a general-purpose optocoupler, not a digital isolator.
CTR window and drive current — what 40-80% at 10 mA means
That means at 10 mA LED drive, the output transistor can sink between 4 mA and 8 mA — enough to drive a logic gate input or a low-power relay coil directly. The 300 mV max Vce saturation keeps the on-state voltage drop low, so the output stays in the linear region for the full 50 mA rated output current. For designs that need tighter CTR binning, the CNY17 family offers graded options; the 'SD' suffix here is the standard wide-bin part.
The gull-wing leads are surface-mount, compatible with standard reflow profiles. Tape & Reel packaging suits automated pick-and-place.