MAXREFDES62#: RS-485 communication micro PLC card

Introduction

Industry 4.0¹ marks the fourth industrial revolution, characterized by distributed, intelligent control systems. Breaking from a past with large, centralized programmable-logic controllers, Industry 4.0 allows for highly configurable, highly modular factories that accept an ever-increasing number of sensor inputs and operate at a higher output than before. The ultra-small PLC, or Micro PLC, lies at the heart of the Industry 4.0 factory, providing high performance with ultra-low power consumption, in an ultra-small package. The MAXREFDES62# is Maxim’s micro PLC RS-485 communications card.

The MAXREFDES62# features two RS-485 transceivers (one full duplex and one half duplex) with isolated power and data. Each driver output has a selectable 120Ω termination resistor. The MAXREFDES62# design integrates one half-duplex RS-485 transceiver (MAX14783E); one full-duplex RS-485 transceiver (MAX14789E); 600V_RMS data isolation (MAX14850); a STM32F1 microcontroller; a FTDI USB-UART bridge; and isolated/regulated +3.3V power rails (MAX17498C/ MAX17515). The entire system typically operates at less than 500mW and fits into a space roughly the size of a credit card. While targeted for industrial and micro PLC applications, the MAXREFDES62# can be used in any application that requires high RS-485 data rates and ESD protection. A block diagram is shown in Figure 1.

Figure 1. The MAXREFDES62# reference design block diagram.

Features

• High-speed RS-485 communication
• Isolated power and data
• Micro PLC form factor
• Extended Protection with TVS on RS-485 Lines
• Device drivers
• Example C source code
• Test data

Applications

• Industrial control and automation
• Process control
• PLC