In industrial control, industrial automation, motor control, and process automation applications, binary/digital sensors and switches are frequently required. Systems often need many optocouplers for isolating each sensor channel. The Corona (MAXREFDES12#) subsystem reference design provides the front-end interface circuit of a programmable logic controller (PLC) digital input module. The serialization feature allows a large reduction in the number of optocouplers used for isolation. The reference design accepts high-voltage inputs (36V, max) and features isolated power and data—all integrated into a small form factor. The Corona design integrates an octal, digital input translator/serializer (MAX31911), a data isolation device (MAX14850), and an H-bridgetransformerdriver for isolated power supply (MAX13256). The Corona digital input circuit solution is mainly targeted for digital input modules for PLCs, industrial automation, process automation, and motor control applications.