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EETE MAY 2013

POWER COMPONENTS Intelligent diagnostics maximize factory-floor up-times By Hubert Baierl More than often it is common that when technical equipment fails, finding the root cause of the failure consumes significantly more time than actually fixing the problem. In highly sophisticated factory automation environments where capital intensive equipment is in operation or where time-coupled chemical processes are at work, line-downs can have substantial implications on the commercial viability of the enterprise. Therefore, the days of machinery providing no diagnostic feedback are becoming obsolete. Solutions that can provide intelligent diagnostic feedback as the system is beginning to fail (“preventive maintenance”) or when a hard failure has occurred (“repair”) are key to reducing expensive unscheduled downtimes. Power management with built-in diagnostics The ISO2H823V is a power management integrated circuit with built-in intelligent diagnostic functions designed for use in a wide range of industrial control applications, including Programmable Logic Controllers (PLCs), Distributed Control Systems, Robotics and many more. This 8-channel high-side driver IC features integrated 2.5kVrms galvanic isolation, which exceeds the IEC 61131-2 requirements for reinforced isolation. Concurrently, the device sets a new standard for system-level diagnostics. Each of the 8 channels is equipped with five-fold diagnostic monitoring capabilities: Open Load Active (OLA), Open Load Inactive (OLI), Short-to-Vbb, Over Current and Over Temperature. Additionally five types of diagnostic feedback on the IC-level are provided. This is all integrated into a small 12x12 mm VQFN package. In the industrial control system, thanks to the integrated galvanic isolation, the ISO2H823V is positioned between the 3.3V micro-controller domain (“control side”) and the 24V factory floor domain (“process side”). The most frequent failure mechanisms on the application level include overload of the driver outputs or actually having no load (“open load”) connected to the driver outputs. Another severe deficiency is lack of or insufficient supply of the 24V Vbb on the on the factory side of the system. The ISO2H823V can detect either of these problems and many more. This capability is highly valuable for OEMs to prompt preventive maintenance and in case of malfunctions to drastically reduce the time required for repair. The benefit for the system designer rests in the fact that many powerful diagnostic capabilities are available in the single IC. This eliminates the need to develop complex and potentially cumbersome circuit layouts based on multiple discrete components, to be able to perform diagnostic monitoring. In consequence, system design efforts, risks and time are reduced substantially, PCB area can be kept small, and the reliability of the solution is not compromised. Fig. 1: Line-downs can have substantial implications and early diagnostic feedback can limit potential losses. Five types of diagnostics for each individual channel: Overload OCL Wear-out of machinery may lead to an output overload. In its extreme form there is actually a short circuit to GND caused either by erroneous wiring, short-circuit during operation or a natural disaster which leaves the equipment flooded, i.e. it literally is under water. The ISO2H823V can detect such cases. When the switch of a channel is “on”, that channel’s output current is monitored. If the output current exceeds the threshold to activate the current limitation, typically set at 1A, then Over Current Limitation (“OCL”) is flagged to the micro-controller – see figure 2. Unlike other products, the ISO2H823V provides not only overload feedback, but it also informs the system controller which channel is subjected to the overload. This information can be instrumental to identify the root cause, which is critical to getting the system back on line within the shortest time possible. Open load OLA Mechanical strain, e.g. vibration or excessive bend stress of a cable, as well as corrosion can lead to the wiring between the IC switching output and the load to become high-ohmic or even disconnected (“wire-break”). The ISO2H823V can detect such circumstances. The IC performs output current monitoring, but not only for the purpose of limiting the maximum output current. The same capability is used to detect “no load” situations. An Open Load Active (“OLA”) feedback is provided if an output is turned on and the output current of an individual channel is less than 0.5mA to 3mA - see figure 3. The system hardware design has the freedom to set the triggering threshold level within this range. No other driver product designed for the industrial control Hubert Baierl is Senior Business Manager at Infineon Technologies – www.infineon.com www.electronics-eetimes.com Electronic Engineering Times Europe May 2013 17


EETE MAY 2013
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