Digital power will change your board

To make things even more complicated some advanced processor types can be powered by different supply voltages when in different modes, to save power. Multiple power rails with advanced algorithms for power management are therefore required for the different sub-systems.

The solution to achieving the best possible efficiency despite these complex demands is to use intelligent digital control techniques to monitor and control the DC/DC converters supplying different sub-systems. With digital control, adaptive voltage scaling and automatic compensation are possible - efficiency can be increased for conditions such as low-load, which reduces heat generation and the amount of energy required, and therefore reduces cost. Although digital power architectures were conceived in the data centre and telecoms sectors, issues such as improving efficiency at low-load are relevant across the whole of the industry.

A digital power management system consisting of power supplies (slaves) connected to a controller (master) via a communications bus depicted by the yellow lines

With the advent of digital power, power modules have become a lot more complex, and manufacturers have developed their own proprietary software and control schemes. Although digital products perform better than previous generations, it is no longer easy to swap a DC/DC converter for a design with one from a different manufacturer. This issue is important for the power supply industry, which wishes to ensure multiple sources are available for each product to assure customers of the reliability of the supply chain while promoting customer choice.

In the past, industry bodies such as POLA and DOSA specified standardised footprints, form factors and pin-outs that products could conform to in order to establish multiple sources for similar products, with DOSA even standardising footprint, form factor and pin-out for digitally controlled DC/DC converters. However, the DOSA standard did not address software related issues. For a digital power supply to truly be a second source for another company’s product, the software and interfaces have to be entirely compatible so that one product is a direct replacement for another. A level of software compatibility is necessary, including compatibility of PMBus commands, proprietary controller commands and configuration files for true plug-and-play compatibility.

Seeing this problem, several leading manufacturers put their heads together and decided to form a consortium to standardise some aspects of digital power, with a view to creating alternative sources for each other’s products. The Architects of Modern Power group (AMP) say that standardisation will help to accelerate innovation and efficiency improvements in their products, but all the companies involved will continue to offer a variety of products in a range of densities and footprints, and with a variety of features.

AMP’s member companies, CUI, Ericsson Power Modules and Murata Power Solutions, introduced its first set of standards for digital POL converters and advanced bus converters at electronica 2014. The standards detail mechanical footprints, features and configuration files for several classes of product.

The first two new standards, microAMP and megaAMP, are for 20-25A and 40-50A POL converters, respectively. Horizontal and vertical configurations are available for both. All products compatible with these standards are interchangeable. For example, mega AMP-50 compatible products like CUI’s NDM2Z series are a viable second source for both Ericsson Power Modules’ BMR464 series and Murata Power Solutions’ OKDx-T/50 series.

MergaAMP-50 compatible 50A POL converters. L-R CUI NDM2Z series, Ericsson Power Modules BMR464 series, and Murata Power Solutions OKDx-T/50 series

The second two standards, ABC-ebAMP and ABC-qbAMP, are for advanced bus DC/DC converters. ABC-ebAMP is for 58.42x22.66mm eighth brick supplies ranging from 264 to 300W. ABC-qbAMP is for quarter bricks (58.42x36.83mm) between 420 and 468W. ABC-qbAMP compatible products include CUI’s NQB-D series, Ericsson Power Modules’ BMR456 series and Murata Power Solutions’ DRQ series, which are all suitable second sources for each other.

ABC-qbAMP compatible advanced bus converters. L-R: CUI NQB-D series, Ericsson Power
Modules BMR456 series and Murata Power Solutions DRQ series.

Although they can be replaced by each other, AMP-compliant products may still be differentiated from each other based on certain aspects of performance, and price.

The AMP consortium plans to continue to work closely with customers to understand their requirements, and with partners such as digital controller manufacturers, in order to jointly define and develop a roadmap for the distributed power architecture designs of the future.

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