Digital isolation for logic-level interfaces
The onsemi HCPL0700R2 is a single-channel optocoupler that bridges a DC input to a Darlington transistor output with base access, providing 2500Vrms galvanic isolation between two circuit domains. With a current transfer ratio spanning 300% minimum to 2600% maximum at a 1.6mA forward current, this part drives logic-level loads directly from a low-current LED input — the wide CTR range accommodates LED degradation over temperature and lifetime without losing the logic threshold. The Darlington output stage delivers up to 60mA per channel at a maximum output voltage of 7V, making it suitable for interfacing 3.3V or 5V logic families to higher-voltage or noisy backplanes while maintaining isolation.
Switching speed and signal integrity
Typical turn-on time is 1µs and turn-off time is 7µs, which sets the data rate ceiling at roughly 100 kbps for a 50% duty-cycle signal — adequate for status feedback, fault detection, and slow serial buses like I²C or SMBus, but not for high-speed SPI or CAN. The base terminal on the Darlington output allows the designer to add a pull-down resistor or a speed-up capacitor to tailor the turn-off edge — a common technique when driving a PLC input module that expects a specific edge rate.