13.9 kVDC isolation — creepage and clearance for high-voltage barrier
The CNY65ST is a single-channel Vishay optocoupler with a transistor output, rated for 13,900 VDC of isolation between input and output. That isolation voltage is the dielectric withstand rating — it certifies the galvanic barrier for applications where the primary and secondary circuits must be electrically separated, such as in medical equipment, industrial power supplies, or motor drive feedback paths where transient overvoltages could otherwise couple across the barrier. The 4-SMD gull wing package (supplier device package 4-SMD) places the optocoupler in a surface-mount footprint suited for automated assembly. The gull-wing leads provide a visible solder joint for inspection, which is relevant for high-reliability builds where post-reflow optical inspection is required.
CTR range 50% to 300% at 5 mA — drive margin and aging headroom
The wide 6:1 spread between min and max is typical for phototransistor optocouplers; the design must tolerate the full range without saturating the output or starving the load. The output transistor is rated for a maximum collector-emitter voltage of 32 V and a continuous output current of 50 mA per channel. Vce saturation is 300 mV maximum, which keeps the voltage drop low when the transistor is fully on — important for maintaining logic-low levels in digital signal isolation.
Switching speed and temperature range
Rise and fall times are 2.4 µs and 2.7 µs typical, with turn-on and turn-off times of 5 µs and 3 µs typical. These figures place the CNY65ST in the standard-speed phototransistor class — suitable for DC signal isolation, status feedback, and low-frequency data transmission up to roughly 100 kHz. For higher-speed interfaces such as fieldbus or isolated SPI, a digital isolator or high-speed optocoupler would be required. The forward voltage is 1.32 V typical at rated current, and the maximum DC forward current is 75 mA — the LED drive circuit should be designed to stay well below this absolute maximum, typically at 5 mA to 20 mA for the CTR window.