Maxim > Design Support > Technical Documents > Sub-System Boards > APP 5611 Keywords: Corona, MAXREFDES12, subsystem reference design, digital input translator/serializer, digital input modules, PLC, home automation, industrial automation, process automation, motor control, isolated power and data SUB-SYSTEM BOARD 5611 Corona (MAXREFDES12 ): Isolated Industrial Octal Digital Input Translator/Serializer May 20, 2013 Abstract: This document explains how the Corona (MAXREFDES12 ) subsystem reference design provides a compact and simple isolated digital input interface for industrial control and automation applications. Hardware and firmware design files are provided. Introduction 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 More detailed image (PDF, 5.9MB) 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 dataall 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. Figure 1. The Corona subsystem design block diagram. Page 1 of 6Features Applications Eight high-voltage input channels (36V, max) Building automation On-chip 8-to-1 serialization with SPI interface Digital input modules for PLCs On-chip 5V regulator Industrial automation Isolated power and data Motor control Small printed circuit board (PCB) area Process automation Device drivers Example C source code Pmod -compatible form factor Detailed Description of Hardware The Pmod specification allows for both 3.3V and 5V modules as well as various pin assignments. This module works with either 3.3V or 5V supply voltages and uses the SPI pin assignments as illustrated. The power requirements are shown in Table 1. The currently supported platforms and ports are shown in Table 2. Table 1. Power Requirements for the Corona Subsystem Reference Design Power Jumper Power Input Voltage Input Current (mA, Type Shunt Name (V) typ) 3.3 19.4 U3 VCAA 5 27.2 Isolated JU1: 12 power 12 13.6 U1 VCC24V 24 14.5 3.3 19.4 U3 VCAA 5 27.2 Field JU1: 2-3 power 12 8.2 U1 VCC24V 24 8.2 Table 2. Supported Platforms and Ports Supported Platforms Ports JA1 Nexys 3 platform (Spartan -6) JA1 ZedBoard platform (Zynq -7020) The Corona subsystem is an isolated, octal, digital input translator/serializer. The design includes an octal, digital input translator/serializer (MAX31911), an H-bridge transformer driver (MAX13256), and a six-channel digital isolator (MAX14850). The MAX31911 (U1) industrial interface serializer translates, conditions, and serializes the 24V digital output of sensors and switches used in industrial, process, and building automation to CMOS-compatible signals required by microcontrollers. It provides the front-end interface circuit of a PLC digital input module. The device features integrated current limiting, lowpass filtering, and channel serialization. Input current limiting allows a significant reduction in power consumed from the field voltage supply as compared to traditional discrete resistor-divider implementations. Selectable on-chip lowpass filters allow flexible debouncing and filtering of sensor outputs based on the application. On-chip serialization allows a large reduction in the number of optocouplers used for isolation. For enhanced robustness with respect to high-frequency noise and fast electrical transients, a multibit CRC code is generated and transmitted through the SPI port for each 8 bits of data. The on-chip 5V voltage regulator can be used to power external optocouplers, digital isolators, or other external 5V circuitry. The MAX13256 (U2) provides an isolated, functional insulation class power solution that accepts an 7.6V to 36V DC supply, and converts it to an isolated 7V to 36V DC supply with an off-the-shelf TGMR-501V6LF Halo transformer with a 1:1 primary to Page 2 of 6