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28 April 2008

ESMexpress, System-On-Module Standard for Harsh Environments

With the ESMexpress standard MEN Mikro Elektronik bridges a gap in the market for system-on-modules for harsh environmental conditions and safety-critical requirements in industrial embedded applications. Unlike the COM Express standard which is administered by the PICMG, ESMexpress is currently prepared to be standardized according to ANSI by the VITA. The official designation is ANSI-VITA 59, RSE Rugged System-On-Module Express.

FIELDS OF APPLICATION

System-On-Modules (SOM) or Computer-On-Modules (COM) are complete computers on a plug-on module. By configuring the I/O on an individual carrier board the functionality can be tailored to the application, thus saving costs and time-to-market.

The ESMexpress standard has been developed for applications requiring highly robust electronics which ensure safe and reliable operation even in harsh environmental conditions. This applies in particular to railway and avionics applications, partially to industrial automation and medical engineering as well as mobile applications in general.

TECHNICAL ASPECTS

Therefore, during the development of ESMexpress, the main focus was on the fanless cooling concept that is prepared for a power dissipation of up to 35 Watts and support of both conduction and convection cooling. To achieve this, the populated PCB is mounted into a frame and completely enclosed in an aluminum housing. The high pressure caused by the screw joints between the housing and the PCB supports the thermal connection of the components.

If the power dissipation of the respective ESMexpress module necessitates additional cooling measures, the housing is either connected to an external heat dissipation system (conduction) or combined with a heat sink for heat dissipation (convection). At the same time the housing ensures optimum EMC protection for the electronic parts.

Another important point is the resistance against shock and vibration. For this, the module is fixed onto the carrier board using eight screws, a connector is used which is specified for MIL and railway applications and supports differential signals with up to 8 GHz. The mechanically robust connector has a stacking height of 5 mm with a minimum tolerance of +/-0,3 mm, is equipped with fixedly assigned contacts for power supply and is specified for an operating temperature of -55°C to +125°C.

The electrical signals are distributed on two 120-pin connectors and are only defined for the modern serial buses. For PCI Express there are four single lane ports (4×1) and one port which can be configured as 1×16, 1×8, 2×4 oder 2×1.

In addition there are three one-Gigabit Ethernet (also as 10-Gigabit), eight USB, three SATA, SDVO, LVDS, HD Audio, several utility signals and the single 12V power supply. The pin assignment is fixed without allowing options in order to guarantee the interchangability of the ESMexpress modules.

Regarding the processor architecture ESMexpress is completely open, as long as the maximum power dissipation of 35W is not exceeded. Of course, all Intel platforms can be used, like the new UMPC family starting with the Intel Atom or the Intel Core architecture with the mobile chipsets, e.g. Core 2 Duo with 965GME. Just as well suited are PowerPC-CPUs, e.g. the MPC8548 from the PowerQUICC-III family by Freescale.

COMMERCIAL ASPECTS

In order to achieve an attractive price for the ESMexpress modules, mechanical components like the frame or the heat sink have been standardized as much as possible and will be available on the market as standard products. Independent of the functionality of the module and the field of application, the module can also be used without a housing.

Cost savings regarding the electronic parts can be achieved via the fully-automated production of the 100% SMD modules. Depending on the module function one of the two 120-pin connectors can be omitted. In addition, the occasionally required connection of additional individual I/O via IP cores in an FPGA has also been moved to the carrier board to save costs.

Being an ANSI standard, ESMexpress offers even more advantages, e.g. cost reduction because of shorter development times or easy exchangeability of discontinued components in critical applications with a required long-time availability of 15 years and more.

Finally, ESMexpress is compatible with COM Express, regardless of the different concept. Via an adapter board which complies with the COM.0 Basic Form Factor Type 2 and adapts the mechanics and the pinout, ESMexpress modules can be used on COM Express carrier boards. Vice versa it is possible to prepare carrier boards for both COM Express and ESMexpress modules.

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