Current Transfer Ratio — the real design margin
The CNY17F3SR2M: CTR is specified at 100% minimum and 200% maximum at If=10mA, Vce=5V. The 400mV Vce(sat) ceiling at 50mA output ensures the output stays in saturation across the load range.
Temperature range and package — board-fit note
The 6-SMD Gull Wing footprint sits flat on the solder paste for standard reflow.
Sourcing posture — active, no LTB on record
For a BOM cost engineer: the surface-mount reel variant (SR2) is the most widely stocked format; the through-hole CNY17F3M is a pin-compatible alternative.