System Board 5879

MAXREFDES36#: IO-Link 16-Channel Digital Input Hub



MAXREFDES36# System Board Enlarge+

Introduction

Programmable logic controllers (PLCs) and distributed control systems (DCSs) use more digital inputs than any other input signal type combined. Running wires in parallel back to the PLC for industrial digital inputs is not only expensive but also creates a wiring rat’s nest that is difficult to maintain. Field buses improved the situation considerably by moving the I/O interface from the PLC to a remote I/O hub mounted close to the field sensors. However, the lack of a single, universally accepted field bus has also created confusion, training challenges, high costs, and compatibility issues among equipment.1

IO-Link is the first open, field bus agnostic, low-cost, point-to-point serial communication protocol used for communicating with sensors and actuators that has been adopted as an international standard (IEC 61131-9).2 IO-Link finally standardizes interoperability of industrial equipment from all over the world. IO-Link can function directly from the PLC or can be integrated into all standard field buses, quickly making it the defacto standard for universally communicating with smart devices like the MAXREFDES36#.

The MAXREFDES36# is an IO-Link 16-channel digital input hub that fits on a small 53.75mm x 72mm printed circuit board (PCB). Maxim Integrated and Technologie Management Gruppe Technologie und Engineering (TMG TE) collaborated in designing the MAXREFDES36# as an IO-Link version 1.1/1.0 compliant digital input hub reference design. The MAXREFDES36# design consists of an industry standard Maxim Integrated IO-Link device transceiver (MAX14821), an efficient high-voltage step-down converter (MAX17552), a Renesas® ultra-low-power 16-bit microcontroller (RL78) utilizing TMG TE’s IO-Link device stack and two Maxim Integrated digital input serializers (MAX31913). Figure 1 shows the system block diagram.


Figure 1. The MAXREFDES36# reference design block diagram.

Features

  • DIN rail form factor
  • IEC 61131-9
  • IO-Link version 1.1 and 1.0 compliant
  • On-chip 8:1 serialization
  • Fault monitoring
  • Field powered LED drivers

Competitive Advantages

  • Small size
  • Low power
  • Low cost

Applications

  • Digital input modules for PLCs
  • Assembly lines
  • Conveyor systems
  • Robotics
  • Process control and automation
  • Industrial automation
  • PLC and DCS systems

Detailed Description of Hardware

The MAXREFDES36# IO-Link 16-channel digital input hub is made up of four main blocks: IO-Link transceiver, step-down converter, digital input serializers, and microcontroller as shown in Figure 1.

The MAX14821 IO-Link device transceiver is IO-Link version 1.1/1.0 physical layer compliant with configurable outputs (push-pull, pnp or npn), reverse-polarity/short-circuit protection, extensive fault monitoring all in a tiny 2.5mm x 2.5mm WLP package.

The MAX17552 high-voltage synchronous step-down converter efficiently converts 24V to 5V with an ultra-small footprint.

The MAX31913 is an octal digital input serializer with LED drivers for input port indication. Other features include configurable input current limiting, fault monitoring, and an internal 5V regulator. There are two cascaded MAX31913 devices on the board allowing 16 digital inputs.

An ultra-low-power RL78/G1A microcontroller with current consumption down to 66µA/MHz provides system control. It features 64kB on-chip programmable flash memory, 4kB on-chip data flash, and operates down to 1.8V, all in a tiny 3mm x 3mm LGA package.

Transient voltage suppressor (TVS) diodes are not all equal. The SDC36 TVS diodes have a clamping voltage less than 55V and meet both IEC 61000-4-2 (ESD) and IEC 61000-4-4 (EFT). There are many smaller TVS diodes on the market that cannot meet these specifications.

Push-in terminal blocks are used for all sixteen digital inputs, 24V, and ground. The 24V is provided by the IO-Link master and provides a minimum of 200mA per the IO-Link specification. The PCB fits in an enclosure with an industry standard DIN rail clip at the back as shown in Figure 2a.


Figure 2a. The MAXREFDES36# reference design has a DIN rail clip.

The MAXREFDES36# uses an industry standard M12 connector allowing a 4-wire, or the conventional 3-wire, cable to be used, keeping costs low. The MAXREFDES36# consumes less than 10mA (typ).

Detailed Description of Software

The MAXREFDES36# was verified using TMG TE’s TMG IO-Link Device Tool V3, which comes with the purchase of the TMG-USB IO-Link master TS hardware. Contact TMG TE for more information. It was also verified using Balluff’s IO-Link Device Tool version 2.11.1, which comes with the purchase of the Balluff USB IO-Link master, part number BNI USB-901-000-A501 (see Figure 2b). Contact Balluff or one of their local distributors for ordering information. Download the IODD file (*.xml) located in the All Download Files section at the end of this document and go to the Quick Start section below for step-by-step instructions on how to use the software. Figure 3 shows a screen shot of the Balluff IO-Link Device Tool.


Figure 2b. The MAXREFDES36# reference design connected to a Balluff USB IO-Link Master.


Figure 3. Balluff’s IO-Link Device Tool version 2.11.1.

Detailed Description of Firmware

The MAXREFDES36# ships pre-programmed as a working IO-Link digital input hub ready to connect to an IO-Link master. The firmware targets a Renesas RL78 microcontroller and follows the simple flow chart shown in Figure 4. The firmware is written in C using the IAR embedded workbench from IAR Systems and utilizes TMG TE’s IO-Link device stack.


Figure 4. The MAXREFDES36# firmware flow chart.

Detailed Description of Firmware

After hot plug-in, the MAXREFDES36# waits for a wake-up signal from the IO-Link master. After receiving the wake-up signal, the MAXREFDES36# synchronizes to the IO-Link master’s 230.4kbps baud rate (COM3). Communication parameters are exchanged. The MAXREFDES36# then starts a cyclic data exchange every 1ms by sending the sensor process data to the IO-Link master. If the sensor is removed, the IO-Link master will detect a missing sensor.

Detailed Description of Use Cases

There are two different use cases that you should consider before purchasing MAXREFDES36#. Use case 1 is simply using the MAXREFDES36#, which is pre-programmed to connect with a user-supplied IO-Link master and IO-Link cable as shown in Figure 5. Use case 2 is where the entire firmware development system is needed as shown in Figure 6.


Figure 5. Use case 1 is the MAXREFDES36# quick start system.

Table 1. Recommended Components Needed for Use Case 1

Use Case 1 (MAXREFDES36# Quick Start System)
Company Description Orderable Part Number
Maxim Integrated IO-Link Digital Input Hub (ships programmed) MAXREFDES36#
Balluff USB IO-Link Master BNI USB-901-000-A501
Balluff IO-Link Cable (4-wire/2m) BCC05MC

 


Figure 6. Use case 2 is the MAXREFDES36# firmware development system.

Table 2. Recommended Components Needed for Use Case 2

Use Case 2 (RL78 IO-Link firmware development system—Renesas Starter Kit for RL78/G1A)
Company Description Orderable Part Number
Renesas Electronics Renesas Starter Kit for RL78/G1A
Includes:
IAR Embedded Workbench for Renesas RL78
Santa Cruz (MAXREFDES23#)
Programming Adaptor (MAXREFDES23DB#)
YRL78IOLINKMAX
Maxim Integrated IO-Link 16 Channel Digital Input Hub
(ships programmed, but is reprogrammable)
MAXREFDES36#
Renesas Electronics E1 Programmer/Debugger R0E000010KCE00
Balluff USB IO-Link Master BNI USB-901-000-A501
Balluff IO-Link Cable (4-wire/2m) BCC05MC

 

Source code is only provided with use case 2, which is the Renesas Starter Kit for RL78/G1A. Contact Renesas Electronics for more information.

Quick Start (Use Case 1)

Required Equipment:

Purchased from Maxim:

  • MAXREFDES36# board

User supplied:

  • Windows® PC with a USB port
  • Balluff USB IO-Link master, part number BNI USB-901-000-A501
  • Balluff IO-Link Device Tool (tested with version 2.11.1 and comes with IO-Link master)
  • M12 4-pin or 3-pin IO-Link cable (BCC05MC)

Note: Verify with Balluff that your version of Windows is supported before purchasing their software.

Download, read, and carefully follow each step in the MAXREFDES36# Quick Start Guide.

Lab Measurements

Equipment Used:

  • Windows 7 PC with USB port
  • MAXREFDES36# board
  • Programming adapter (MAXREFDES23DB#) board
  • Balluff USB IO-Link master, part number BNI USB-901-000-A501
  • Balluff IO-Link Device Tool (tested with version 2.11.1 and comes with IO-Link master)
  • M12 4-pin or 3-pin IO-Link cable
  • RD36_RL78_V01_00.ZIP (IODD file); where XX_XX = latest version from webpage
  • Fluke 189 Multimeter
  • Tektronix® TDS2024B—4-channel 200MHz/2Gsps oscilloscope

Figure 7 shows the typical total hub current for changing values of both hub-powered digital input codes as well as for the more common field-powered digital input codes. The point of this figure is to show that the MAXREFDES36# provides field-side LED drivers, requiring no power from the hub. Figure 8 shows an oscilloscope screen shot of the cyclic data exchange every 1ms from the MAXREFDES36# to the IO-Link master.


Figure 7. MAXREFDES36# HUB CURRENT vs. HUB-POWERED INPUT CODE vs. FIELD-POWERED INPUT CODE, IO-Link Power = 24V, at room temperature.


Figure 8. Cyclic data exchange every 1ms from the MAXREFDES36# to the IO-Link master.

References

  1. Fieldbus Inc's IEC61158 Technology Comparison study, Slide 58: "Fieldbus Technology Challenges".
  2. IO-Link System Description 2013 by IO-Link Company Community. Page 3, Preface.

Fluke is a registered trademark of Fluke Corp.
IO-Link is a registered trademark of ifm electronic GmbH.
Renesas is a registered trademark and registered service mark of Renesas Electronics Corp.
Tektronix is a registered trademark and registered service mark of Tektronix, Inc.
Windows is a registered trademark and registered service mark of Microsoft Corp.

Quick Start (Use Case 1)

Required Equipment:

Purchased from Maxim:

  • MAXREFDES36# board

User supplied:

  • Windows® PC with a USB port
  • Balluff USB IO-Link master, part number BNI USB-901-000-A501
  • Balluff IO-Link Device Tool (tested with version 2.11.1 and comes with IO-Link master)
  • M12 4-pin or 3-pin IO-Link cable (BCC05MC)

Note: Verify with Balluff that your version of Windows is supported before purchasing their software.

Download, read, and carefully follow each step in the MAXREFDES36# Quick Start Guide.

 

Related Resources

MAX14821
IO-Link Device Transceiver

  • IO-Link Specification v.1.0 and v.1.1 Physical Layer-Compliant
  • Supports COM1, COM2, and COM3 Data Rates
  • IO-Link Device Wake-Up Detection

MAX31913
Industrial, Octal, Digital Input Translator/Serializer

  • Eight High-Voltage Input Channels (36V max)
  • Configurable for IEC 61131-2 Input Types 1, 2, 3
  • Wide Operating Supply Range of 7V to 36V

MAX17552
60V, 100mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter with 22μA No-Load Supply Current

  • Eliminates External Components and Reduces Total Cost
  • Reduces Number of DC-DC Regulators to Stock
  • Reduces Power Dissipation