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-bridge transformer driver 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.