MAXREFDES79

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).1 IO-Link finally standardizes interoperability of industrial equipment from all over the world. IO-Link can function directly from the PLC or can be converted from all standard field busses to IO-Link through a gateway, quickly making it the defacto standard for universally communicating with smart sensors and actuators.

IO-Link is a Single-drop Digital Communication Interface (SDCI), which means there can only be one sensor or actuator per port. The 3-wire protocol is also backwards compatible with binary sensors and actuators that use standard input output (SIO). IO-Link Device Descriptor (IODD) files completely define the device and eliminate manual parameterization.

Maxim Integrated and TEConcept collaborated in designing the MAXREFDES79# IO-Link master using TEConcept’s IO-Link master stack. It is a version 1.1-compliant IO-Link master reference design. The MAXREFDES79# design consists of four industry-standard Maxim Integrated IO-Link master transceivers (MAX14824), two efficient industrial step-down converters (MAX15062B, MAX17552), and an STMicroelectronics 32-bit ARM Cortex M4 microcontroller (STM32F4) utilizing TEConcept’s TC Tool software and IO-Link master stack. Figure 1 shows the system block diagram.

The MAXREFDES79# IO-Link master consists of 4 main blocks: four IO-Link master transceivers, step-down converters, microcontroller, and USB connection as shown in Figure 1. The MAX14824 IO-Link master transceiver is IO-Link version 1.1/1.0 physical layer compliant with highly integrated 5V and 3.3V linear regulators, configurable outputs (push-pull, high side or low side), auxiliary digital input, 300mA C/Q output drive, and reverse-polarity/short-circuit protection, all in a small 4mm x 4mm, industrial-friendly TQFN package.

The MAX15062B is a high-voltage, synchronous step-down converter that efficiently converts 24V to 5V in a tiny 2mm × 2mm, 8-pin TDFN package. The circuit defaults to PWM operation to maintain a constant frequency during all operating loads. Removing resistor R502 will put the MAX15062B into PFM mode. This reference design features optimal efficiency with PWM operation, selecting PFM mode will not provide any benefit.

Rather than use a linear regulator to drop 5V to 3.3V, the MAX17552 synchronous step-down converter efficiently converts 5V to 3.3V using a small 3mm x 2mm, 10-pin TDFN package. The MAX17552 circuit is optimized for the smallest component size and a lower input voltage range allowing the use of a 2.95mm × 2.95mm inductor instead of a 4.8mm × 4.8mm inductor. Placing the MAX17552 in series with the MAX15062B allows the MAX17552 to utilize the MAX15062B’s larger input range (up to 60V) while using the smaller inductor. The architecture uses an additional 10mW. If power efficiency is the highest priority in your design, remove resistor R503 to select PFM mode on the MAX17552 to save approximately 3mW of power. The frequency will no longer be fixed in that case.

An STM32F4 ARM Cortex M4 microcontroller in a 10mm × 10mm, 64-pin LQFP package provides system control. A universal serial bus (USB) port was implemented using the STM32F4’s internal USB peripheral and STMicroelectronic’s VCP driver.

For protection, the MAXREFDES79# features both Schottky and SMA transient voltage suppressor (TVS) diodes at the IO-Link interface. At the power-supply input, a bidirectional SMC TVS diode clamps over- and undervoltages and a Schottky diode provides reverse-polarity protection.

There are four IO-Link ports and two side-mounted LEDs as shown in Figure 2. The odd number ports are at the top. Power is indicated when the top green LED is on. The lower LED is a red green blue (RGB) LED that indicates the communication status as shown in Table 1.

Figure 3 shows the box contents for the MAXREFDES79# reference design. The MAXREFDES79# box contents are:

• MAXREFDES79# 4-port IO-Link master
• AC-to-DC 24V/1A output power converter
• USA-to-Euro power adaptor
• Two black 1m IO-Link cables
• Micro-USB cable (2m)

Necessary downloadable software includes:

• TEConcept IO-Link Control Tool (CT) software (see Note 1)
• STM32F4 VCP driver (see Note 1)

Figure 4 shows the MAXREFDES79# system connected to a laptop running TEConcept’s CT Tool. The MAXREFDES79# typically consumes 27mA from the 24V supply at 25°C with no sensors attached.

TEConcept CT Windows-compatible GUI software features IODD file import capability, connects to a PC via USB, and is available to download from the Design Resources tab of the MAXREFDES79# webpage. The TEConcept CT software is shown in Figure 5 and a complete step-by-step Quick Start guide is also downloadable from the Design Resources tab.

The TEConcept IO-Link master stack ships preprogrammed inside the MAXREFDES79# hardware with a finite time license displayed by the TEConcept CT software. The MAXREFDES79# ships with more than 9000 minutes of use time. When the time in the Remained time field goes to 0 minutes, the MAXREFDES79# switches off all the IO-Link ports and shows the error message: LICENSEFAULT.

A low-price unlimited time license can be easily purchased from TEConcept GmbH by providing them a valid Hardware ID and Key number. Press the Export hardware ID button located in the License key management window as shown in Figure 6. Provide the hardwareID.txt file when requesting the infinite time license from TEConcept GmbH. Contact info follows for TEConcept GmbH.

TEConcept GMbH Contact Information
BTEConcept GmbH
Wentzingerstr. 21
D-79106 Freiburg
Tel. +49 761 21443640
Fax +49 761 21443631
Email: info@teconcept.de
https://teconcept.de/en/kontakt/

Required Equipment:

Purchased from Maxim:

• MAXREFDES79# (box contents)
• MAXREFDES79# 4-port IO-Link master
• TEConcept IO-Link Control Tool (CT) software (see Note 2)
• STM32F4 VCP driver (see Note 1)
• AC-to-DC 24V/1A output power converter
• USA-to-Euro power adapter
• Two black 1m IO-Link cables
• Micro-USB cable (2m)

User-supplied:

• Windows 7 or Windows 8 PC with a USB port
• IO-Link sensor or IO-Link actuator (see Note 3)

Note 2: Download files from the Design Resources tab

Note 3: Maxim Integrated offers four IO-Link sensor reference designs for immediate operation with the IO-Link master. Please see MAXREFDES23#, MAXREFDES27#, MAXREFDES36#, and MAXREFDES42#.

Download, read, and carefully follow each step in the MAXREFDES79# Quick Start Guide.

IO-Link Compliance Report

The MAXREFDES79# is a fully compliant IO-Link version 1.1 master according to the following test report. It was tested with golden device GD000010. See the test report for details: MAXREFDES79# 4-Port IO-Link Master Test Report.

Equipment used:

• Windows 7 PC with USB port
• MAXREFDES79# (box contents)
• RD79_GUI_V0X_XX_XX_XX.ZIP; where XX_XX = latest version from Design Resources tab on MAXREFDES79 webpage
• MAXREFDES23# (RGB light sensor) port 1
• MAXREFDES27# (proximity sensor) port 2
• MAXREFDES36# (digital input hub) port 3
• MAXREFDES42# (RTD temp sensor) port 4

The lab measurements were taken using the setup and equipment shown in Figure 7.

Figure 8 shows a data plot of the MAXREFDES23# IO-Link RGB light sensor connected to port 1. The sensor is 1in away from a red plastic cup and illuminated by typical ceiling-mount industrial office lights. Figure 9 shows a data plot of the MAXREFDES27# IO-Link proximity sensor connected to port 2 with a white box starting at 250mm away and slowly moving closer to the sensor. The LED current was set to 50mA. Figure 10 shows a data plot of the MAXREFDES36# IO-Link digital input hub connected to port 3 with 24V switched onto channel 1 after 30s. Figure 11 shows a screen shot of the TEConcept CT software reading back the 0x010C Ambient temperature parameter value with the MAXREFDES42# connected to port 4.

References

IO-Link is a registered trademark of ifm electronic GmbH.
ARM is a registered trademark and registered service mark of ARM Limited.
Cortex is a registered trademark of ARM Limited.
Windows is a registered trademark and registered service mark of Microsoft Corp.