The transistor-with-base output allows the designer to bias the base for faster switching or to configure a photodarlington pair externally, giving flexibility in gain and speed trade-offs that a simple phototransistor lacks.
Current transfer ratio and switching speed
CTR is specified at 40% minimum and 80% maximum at If=10 mA. This 2:1 spread means the output current at a given LED drive can vary by a factor of two across units — the design must tolerate the low end or use a feedback loop. Typical turn-on time is 2 µs, turn-off 3 µs, with rise/fall of 4 µs / 3.5 µs max, placing this part in the medium-speed class for 10–100 kHz switching applications.
Package and mounting — surface-mount assembly
Supplied in a 6-SMD gull-wing package on tube, the CNY171SVM is intended for reflow or wave-solder assembly on standard FR-4. The 6-SMD footprint is shared with the through-hole CNY171TVM — a direct drop-in for designs migrating to SMT. The 400 mV Vce saturation at 50 mA output keeps conduction loss low in logic-level interface circuits.