IO-Link: Power Dissipation in Practice

The Limitation of Heat Dissipation

IO-Link is used across many branches of factory automation, and in these applications, areas of the factory floor may experience high ambient temperatures, resulting in both modules & electrical components facing strenuous operating conditions. As Industry 4.0 continues to expand, size becomes increasingly critical as more intelligence is being driven to the edge. In order to develop smaller form factors, heat limitations are a key concern.

Smaller Form Factors & Increasing IO Density

As Industry 4.0 continues to drive intelligence to the edge, IO-Link is seeing increasing demand for use in new environments and in smaller and smaller spaces. This directly challenges the size and capability of every IO-Link sensor and actuator, but it also tangentially impacts the size and density requirements of the IO-Link master gateways.

These gateways often provide 4, 8, or 16 IO-Link master ports, each capable of driving a 500mA load per channel, all while fitting onto a PCB not much larger than an everyday smartphone. This means that power dissipation, and more specifically, the localization of power dissipation, is a key design consideration for determining the amount of heat generated by the module and the reliability of its key electrical components.

Power Dissipation

It is a relatively simple calculation to determine the theoretical power dissipation of an IC based on readily available data from the datasheet. It’s as simple as:

For IO-Link, the specification stipulates that the maximum load current is 500mA per channel. Thus, to calculate power dissipation, one can simply find the On-Resistance of the C/Q Driver, or the applicable voltage drop at 500mA.

In the case of the MAX14819A, the maximum On-Resistance is 2.2Ω.

Taking the equations above, one can estimate that the maximum power dissipation per channel on the MAX14819A is:  

These quick calculations can be a good starting point when comparing two solutions, but as we’ll explore below, you can also directly measure this power dissipation to see how it compares to the theoretical values.

An Example in Practice: MAX14819A

Now, let’s take a more empirical approach and look at power (and heat) dissipation in practice with the MAX14819A  dual IO-Link Master from Analog Devices Inc.

These measurements were taken using ADI’s MAXREFDES165 IO-Link Master Reference design and loaded with 500mA.

1. Measure the voltage present on each channel (V_CQ)with a known load (R_Load = 47.7Ω)
   • MAX14819A = 23.27V
2. Measure the voltage at the supply (V_S)
   • MAX14819A = 23.81V
3. Calculated output current (I = V_CQ/R_Load)
   • MAX14819A = 23.27V / 47.7Ω = 488mA
4. Taking the measured voltage drop (V_Drop = V_S – V_CQ) and output current, calculate the power
   • MAX14819A = (23.81V – 23.27V) x 488mA = 264mW (per channel)

This demonstrates that in practice, the MAX14819A power dissipation remains low, and the performance matches the “typical” power dissipation value quite closely. 

The result of this power dissipation can be seen with a thermal camera where the white area at the center is the MAX14819A which heats to 40˚C after approximately 10 minutes of operation. The ambient temperature was 25˚C during this measurement, giving a generally acceptable temperature delta:

              MAX14819A: ∆T = +15˚C

Figure 1: MAX14819A

The maximum operating temperature of the MAX14819A is 125˚C, and based on these measurements, the IC can operate at industrial-grade ambient temperatures even if all channels operate at their maximum capability.

By minimizing the heat dissipation, designers are able to align with the growing IO-Link adoption trends as was discussed in “IO-Link: Enabling Industrial Connectivity – An Introduction", to shrink form factor and increase intelligence at the edge.

Key Takeaways

Power dissipation is a critical aspect of IO-Link designs. IO-Link gateways are often placed at the edge of the factory floor where operating conditions can reach and sustain high temperatures. If the electronics inside the module generate too much heat, it limits the designers’ ability to shrink the solution size and requires costly implementations, such as heat-sinks.

ADI’s market-leading IO-link solutions, like the MAX14819A, were developed to accommodate these stringent design requirements and keep power and heat dissipation to a minimum.

Before starting your next design, save yourself time and headaches by performing a simple power dissipation calculation and measurement to ensure you are using the best solution.

See all the blogs in the ADIOLINK series.