Server Blade Monitoring And Protection Chip Communicates Over PMBus

March 18, 2010
Product Description of National's LM25066, the first chip to provide PMBus system power monitoring in data-center racks.

LM25066 system power-management and protection IC

National Semiconductor’s LM25066 system power-management and protection IC, which resembles a very smart hot-swap controller, is the first device of its type to apply PMBus to the task. In fact, it simply may be the first device of its type.

The IC’s task is much more comprehensive than hot-swap control, as it’s designed to improve data-center efficiency by facilitating virtualization. PMBus is an open set of standards for power management based on SMBus, an extension of the I2C bus. Without the well-defined command set of the PMBus standard, achieving the functionality of National’s LM25066 would be intimidating.

The LM25066 is aimed at designers of blade servers, storage networking systems, routers and switches, and modular subsystems. While it can turn the intermediate bus on and off autonomously or under external control, its primary virtue lies in its ability to monitor operating parameters. That makes it a useful tool in managing data-center efficiency, as it provides the information necessary to manage virtualization intelligently.

For each blade in the system, the LM25066 continuously supplies the system-management host with real-time power, voltage, current, temperature, and fault data. Specifically, the LM25066 monitoring block measures current and voltage 1000 times per second with 3% current accuracy from –40°C to 125°C. That simultaneous sampling of current and voltage provides a true power measurement for each blade.

The monitoring block also captures the peak current and peak power and computes averages of subsystem electrical operating parameters. At the same time, the temperature-monitoring block can use external diodes to monitor the temperature of the intermediate bus supply’s switching MOSFETs.

In support of the chip’s safety-monitoring function, fault-warning thresholds are programmable, again via the PMBus. Hot-swap support involves both current and power limiting. A suite of development tools helps system designers implement all the features of the part.

The LM25066 comes in a 4- by 5-mm package and costs $5.95 each in 1000-unit quantities.

National Semiconductor

About the Author

Don Tuite

Don Tuite writes about Analog and Power issues for Electronic Design’s magazine and website. He has a BSEE and an M.S in Technical Communication, and has worked for companies in aerospace, broadcasting, test equipment, semiconductors, publishing, and media relations, focusing on developing insights that link technology, business, and communications. Don is also a ham radio operator (NR7X), private pilot, and motorcycle rider, and he’s not half bad on the 5-string banjo.

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