Power Electronics

Are Open Standards Redefining Telecom Power?

Released in December 2002, the Advanced Telecommunications Computing Architecture (ATCA) standard was the first to specifically target telecommunications. Growing demand for features (VoIP, IMS, FMC) on multiple competitive channels (copper, cable, fiber, WiFi, WiMax) drove the need for an open standard to provide greater innovation and performance, shorter development cycles and reduced cost. The challenge was balancing interoperability requirements with sufficient flexibility to allow innovation.

Although most telecom systems were based on -48-V power sources, vendors typically had their own custom/semi-custom board power solutions. Many critical details in ATCA were incorporated from existing UL, NEB and IEC documents to facilitate compliance with existing requirements and ease transition to a new architecture. ATCA boards are powered by dual -48-V supplies with a maximum of 200 W per board.

AMC.0 (2005), another open standard from PCI Industrial Computer Manufacturers Group (PICMG), defines the advanced mezzanine card (AdvancedMC). Powered by up to 150 mA at 3.3 V and up to 6.7 A at 12 V, AdvancedMCs plug into specially designed ATCA “carrier” boards.

These relatively low-cost units could be hot-swapped into carrier boards for upgrades, personalization or repair. To minimize cost, the required hot-swap circuitry was put on the carrier board. To maximize available power to the AdvancedMC, the current limit is specified near the connector's derated limits at a relatively tight ±10% tolerance.

A third standard was released in 2006, MTCA (Micro-TCA). These systems use AdvancedMCs plugged directly into a passive backplane. MicroTCA is a smaller, lighter, less-expensive architecture than ATCA with multiple-chassis form factors and scales.

Of particular interest to the power community is the MicroTCA power module (PM), which must generate and distribute 16 channels of 12 V, and 16 channels of 3.3 V power on a 75-mm × 150-mm module. The source supply could be single or dual ±48 V, ±24 V or line power. The MicroTCA power committee wrestled with power-supply redundancy and came up with some innovative solutions that are made practical by digital power technology, and application-specific ICs controlling AdvancedMCs.

Although still young, these standards have already had an impact. The holdup, ORing and hot-swap requirements of the dual -48-V feeds on ATCA boards have resulted in multiple off-the-shelf modules to provide compliance. Furthermore, several vendors have developed MicroTCA PMs, FPGA-based PM reference designs and ICs to manage power control for AdvancedMCs. This kind of support bodes well for the standards.

Qualification and deployment of ATCA systems is progressing, but slowly. Reasons include general market conditions, learning cycles associated with a new standard and, perhaps most significantly, the hesitancy of telecommunications equipment manufacturers (TEMs) to abandon the tried-and-true in-house architecture for the brand-new public-domain architecture.

However, reluctance to adopt an open standard is tempered by the desire/need to have a seat on the ATCA bus when it takes off. TEMs looking 5 to 10 years down the road do not want to have only proprietary solutions when competitors are using an open standard. Another delaying factor is that many ATCA-based solutions are replacing existing systems. The “no-customer-interruptions” requirement during switchover takes time. However, once installed, there will be multiple competitive suppliers to provide upgrades at reduced cycle times and costs.

Factors driving adoption are constant calls for improved efficiency to address rising energy costs and higher thermal densities. Open standards provide a common target for chassis, IC and other suppliers. Conversely, the market seems to have a strong pull for MicroTCA and other AdvancedMC-based systems. Many applications have no incumbent system to replace, making adoption faster. Also, the cost of entry is lower than that of ATCA.

Are these open standards redefining telecom power? To a degree they already have. As the momentum grows, suppliers become willing to make the investment required to provide highly integrated, efficient solutions. Systems designers see more hardware, software and ICs supporting the market — and the growth continues.

Jim Bird has served on the PICMG, AMC and MicroTCA committees and continues to be active in refining the specifications.

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