Dual-channel optocoupler for isolated signal paths
The HCPL0531 from onsemi is a dual-channel optocoupler with transistor output, housed in an 8-SOIC package. It provides 2500Vrms galvanic isolation between input and output, making it suitable for breaking ground loops and protecting low-voltage logic from high-side transients in industrial control interfaces. Each channel can sink up to 8 mA at the output, with a maximum output voltage of 20 V — enough to drive standard TTL or CMOS logic inputs through a pull-up resistor.
Switching speed and current transfer ratio
Typical turn-on time is 450 ns and turn-off time is 300 ns, which supports data rates in the low-MHz range for isolated serial links or gate-drive feedback. The current transfer ratio is specified between 19% and 50% at a forward current of 16 mA — this range lets the designer calculate the minimum LED drive current needed to guarantee a logic-high at the output across temperature and device variation. Forward voltage is typically 1.45 V at 16 mA, and the absolute maximum forward current is 25 mA, so a series resistor from a logic rail is straightforward to size.