The AdvancedTCA standard issued in 2002 was developed specifically for applications with the highest demands on performance, and the recently issued MicroTCA standard enhances this user spectrum at the lower end. Its form factor and flexible, modular, and scalable construction make MicroTCA an attractive alternative and sensible addition. This is true not only for the telecom sector, where proprietary solutions are being replaced more and more, but also for price-sensitive industry applications.
Extensive application range
MicroTCA is a modular platform, where AdvancedMC modules are assembled directly onto the backplane. Schroff was responsible for the mechanical section of the MicroTCA platform. Its openness and the flexibility to combine AdvancedMCs in a MicroTCA system make it easy to realize different versions. Very small (pico) systems are feasible, in which an AdvancedMC single board computer, an AdvancedMC hard disk, and an AdvancedMC I/O board with an open frame power supply and fans can be combined. Such small systems compete with today’s industrial PC and embedded computer solutions and offer above all modularity, which many users are currently missing. The most efficient systems in the MicroTCA spectrum are represented by the fluid-cooled systems, consisting of several board cages of different heights, with redundant MicroTCA Carrier Hub (MCH) modules, redundant power modules, and three-tier management (carrier, shelf, and system management).
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Subrack solutions or complete systems
MicroTCA is an extension of the 19-inch standard and defines subrack dimensions, power module, the MCH, the shelf management, and use of AdvancedMC modules. Figure 1 shows one example of very simply constructed subracks in 3U for single AdvancedMC modules and in 4U for double AdvancedMC modules. The subracks consist of two side panels, cover and base plate, and an optional rear hood. They are available in 19-inch, as well as in smaller widths for fewer AdvancedMC modules as cube or pico subracks. All these subrack solutions have a depth of 200 mm. Suitable backplanes include those with star or dual-star topology, which support the popular protocols such as GbE, PCI Express, RapidIO, and Serial ATA.
Figure 2 shows a complete MicroTCA system for single or double AdvancedMC modules. The system is equipped with an exchangeable fan tray and air filter, dual-star backplane for redundant MCHs, and space for redundant MicroTCA power supplies. It can easily be adapted for different applications.
The power supplies for the systems convert an input range of
-60 Vdc, -48 Vdc, or 24 Vdc to the +12 V supply voltage specified for the AdvancedMC modules. Developers can build a low-cost solution by combining a MicroTCA input module (single, full-size) from Schroff with a conventional power supply, available on the market. Another option is to have an Open Frame power supply take over the distribution and direct the 12 V supply voltage to the backplane. If redundancy or a higher performance is required, a second power supply can be integrated. The MicroTCA carrier hub combines the hub and management function in one plug-in unit. For some applications in industry, for example self-sufficient control units in a decentralized automation solution, the MCHs can be omitted and small cube and pico subracks used.
Development systems for hardware and software
Systems integrators, as well as hardware and software developers, face an increasing demand for MicroTCA-based applications. Schroff has configured MicroTCA development systems (Figure 3) for AdvancedMC single and double modules. These systems can be used for the development and testing of multiple applications with different MicroTCA system architectures. The MicroTCA development systems are equipped with a 14-slot backplane (2+2+10), two MCH slots, two power module slots for 12 V power supply, and 10 AdvancedMC slots for single or double full-size AdvancedMC modules.
For different configurations further backplanes are available, such as 2+2+12. A hot swappable fan tray with three DC fans together with an easily exchangeable air filter in the front air inlet area provides reliable heat dissipation. An integrated temperature sensor monitors the speed of the fans. For the second power supply, 1U high, pluggable power supply units (redundant) at 300 W each, 12 V/25 A, and a wide range input of 85 Vac up to 264 Vac can be used. Power supply units with an output voltage of -48 V/6.25 A are also available.
Schroff has also developed a single full-size front MicroTCA Power Input Module with +12 Vdc power input that distributes the 12 V delivered from the power supplies to the 16 outputs. The Power Input Module also operates as the source where the defined 3.3 V management voltage is generated and distributed to the 16 outputs. The module is protected against overvoltage, undervoltage, and reverse polarity. In addition, a slot-specific current switch-off ensures the hot swap function, making the plugging of the integrated AdvancedMC modules possible without current. Combining power supplies with a Power Input Module makes an expensive MicroTCA power module unnecessary and keeps costs low for a development and test system.
Clever cooling concepts
Depending on the application, systems integrators can use a wide range of diverse cooling concepts for MicroTCA systems. The standard cooling concept is realized with conventional air cooling. Two flavors of conventional air cooling, push cooling and pull cooling, have advantages and disadvantages.
Cooling solutions can influence the life expectancy, the air stream volume, the air distribution, or the height of the MicroTCA systems. With high-performance losses, when pure air cooling might not be sufficient, the cooling with an air-water heat exchanger from Schroff is an option at cabinet level. For the cooling of high-performance MicroTCA systems at subrack level, Schroff favors direct cooling of the components with a hybrid solution, a combined water and air cooling concept in the chassis. The critical components on the boards are cooled directly with specific water cooling units. The heat, which is generated through the remaining electronic components on the board, can easily be expelled with conventional air cooling.
High availability through redundancy
The very high availability demanded for such systems is guaranteed with redundantly arranged cooling concepts (two cooling units) and power supplies (two power modules) as well as the use of a dual-star backplane with two MCHs. This means events such as the failure of a fan will not affect the operation of the system.
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Cost aspects
Apart from the technical advantages of the new standard, of course, the cost aspects too play an important role. The price range between the low-cost and the high-end solutions is in proportion to the applications’ bandwidths. In the upper performance areas, MicroTCA systems can be compared with AdvancedTCA systems. More affordable low-cost solutions can replace the conventional 19-inch industry PC or embedded solutions. In this way future-proof applications with a smaller form factor are promoted.
MicroTCA combines the advantages of high performance and availability of AdvancedMC and AdvancedTCA technology in one compact system. Using AdvancedMC modules it is possible to create a modular system architecture that is perfectly suitable for scaling, standardization, and customized solutions. For the user the insertion of AdvancedMC modules in MicroTCA systems will result in considerable economies of scale. The rapid increase of AdvancedMC functioning modules for AdvancedTCA and MicroTCA will further support a short time-to-market.
The open standard, modularity, and scalability will result in many customer-specific versions for MicroTCA, which can be adapted very easily from the standard product range.
Volker Haag is leader of Product Development Subracks and Systems at Schroff GmbH, Straubenhardt.
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