MAXREFDES37

Traditional pneumatic actuators have known disadvantages. Air producing equipment adds cost. Furthermore, high pressure air condenses easily, can leak and also can be very noisy. Everyone is familiar with the roar of an air compressor while putting air into a car or bike tire.

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 can directly function from the PLC or can be converted from all standard field busses to IO-Link through a gateway, quickly making it the de facto standard for universally communicating with smart sensors and actuators.

Maxim Integrated and TMG TE collaborated in designing the MAXREFDES37 version 1.1-compliant IO-Link servo driver actuator reference design. The MAXREFDES37 design consists of a Maxim Integrated IO-Link device transceiver (MAX14821), an efficient industrial step-down converter (MAX17504), and a low-power Renesas 16-bit microcontroller (RL78) utilizing TMG TE’s IO-Link device stack. Figure 1 shows the system block diagram.

The MAXREFDES37 IO-Link master consists of 4 main blocks: IO-Link device transceiver, step-down converter, microcontroller, and one of four possible servo motors 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 MAX17504 is a high-voltage, synchronous step-down converter that efficiently converts 24V to 5V in a small 5mm x 5mm, 20-pin TQFN package. The circuit defaults to PFM operation to achieve the highest efficiency during light and heavy loads. It also implements a soft-start to limit inrush current at initial power-up and an active-low RESET output that keeps the microcontroller in reset until the output voltage is stable.

An ultra-low-power RL78/G13 microcontroller with current consumption down to 66µA/MHz provides system control. It features 512kB of flash ROM, 8kB of data flash, 32kB of on-chip RAM, and uses a 5V supply in a HWQFN 7mm x 7mm 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.

The MAXREFDES37 ships with a HiTec HS-53 servo motor and easily plugs into the onboard standard 3-pin headers as shown in Figure 2

Description of Software

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 3 and a complete step-by-step Quick Start guide is also downloadable from the Design Resources tab of MAXREFDES79.

Detailed Description of Firmware

The MAXREFDES37 ships pre-programmed as a working IO-Link servo driver ready to connect to an IO-Link master. The firmware targets a Renesas RL78 microcontroller and follows the simple flowchart 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.

After hot plug-in, the MAXREFDES37 waits for a wake-up signal from the IO-Link master. After receiving the wake-up signal, the MAXREFDES37 synchronizes to the IO-Link master’s 230.4kbps baud rate (COM3). Communication parameters are exchanged. The MAXREFDES37 then starts a cyclic data exchange every 2ms 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 MAXREFDES37. Use case 1 is simply using the MAXREFDES37, which is preprogrammed 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.

Contact Renesas Electronics for more information or questions regarding the RL78/G13.

Quick Start

Required Equipment:

Purchased from Maxim Integrated:

• MAXREFDES37 (box contents)
• MAXREFDES37 board (see Note 1)
• HiTec HS-53

User-Supplied

• Windows 7 or Windows 8 PC with a USB port
• MAXREFDES79# USB IO-Link Master (see Note 1)

Download, read, and carefully follow each step in the appropriate MAXREFDES37 Quick Start Guide.

Lab Measurements

Equipment used: Exactly the same equipment that was used in the MAXREFDES37 Quick Start.

Figure 7 shows a screenshot of the MAXREFDES37’s PWM signal driving the HiTec HS-53 servo motor to 0 degrees. Figure 8 a screenshot of the MAXREFDES37’s PWM signal driving the HiTec HS-53 servo motor to 90 degrees. Figure 9 shows a screenshot of the 20ms period of the MAXREFDES37’s PWM signal. Figure 10 shows a graph of the MAXREFDES37’s 24V line current versus different dynamic servo drive modes and numbers of servo motors.

References

IO-Link System Description 2013 by IO-Link Company Community. Page 3, Preface.

IO-Link is a registered trademark of ifm electronic GmbH.

Windows is a registered trademark and registered service mark of Microsoft Corp.

Renesas is a registered trademark and registered service mark of Renesas Electronics Corporation.