The FOD817ASD provides 5000Vrms isolation between input and output, which qualifies it for mains-referenced feedback loops in off-line power supplies and for isolating logic signals in motor-drive or IGBT gate-drive circuits where the secondary side sits at a high common-mode voltage. The current transfer ratio is specified at 80% minimum and 160% maximum at a forward current of 5mA — this 2:1 spread means the output transistor's collector current for a given input current is guaranteed to fall within that band, so you can size the pull-up resistor at the collector to ensure the output saturates (Vce below 200mV) across the full CTR range and temperature.
Temperature grade and switching speed
Rated for -55°C to 110°C ambient, this part fits industrial control cabinets, outdoor telecom enclosures, and engine-bay-adjacent electronics where the board sees sustained heat — the 110°C ceiling is above the typical 85°C industrial limit, giving margin in a 70°C ambient with self-heating. Rise and fall times are 4µs and 3µs typical respectively — adequate for 10–100 kHz switching power supply feedback or low-speed serial isolation (e.g., 115.2 kbps UART), but not fast enough for high-speed digital isolation where you would look at a logic-output optocoupler.