Powering the infrastructure of the cloud: Page 5 of 6

November 30, 2018 // By Nick Flaherty
Nick Flaherty talks to Chris Mann and Rob Chiacchia at Analog Devices on the power trends for infrastructure for cloud computing, 5G and the Internet of Things and its implications for the next generation PMbus specification and even the Internet from space
on the bus – both Intel and PMbus will be changing the specification to provide multiple rails and not just the core power supply. That wasn’t envisioned in the original spec so a protocol change is being developed right now,” he added.  

Power over Ethernet

Another area that is of growing interest is Power over Ethernet over Category 5 cabling to support the roll out of smaller basestations for 5G cellular networks.

“We are the first to market with a 802.3bt 71W standard based on the PoE+,” said Mann. “Linear Technology was always more forward thinking and always coming up with formats for higher and higher power.”

“The power is really limited by the resistance of the cable so we are working with customers on delivering 150W to the load through PoE++. This is a trend that we are seeing in small cell applications that are powered directly by the Cat 5 cable. A lot of these installations have fixed cat5 or cat6 cables with lower resistance that allows more power to the load. What we see is that small cells will continue to grow,” he said.

“We are seeing a rapid adoption of the ideal diode bridge controllers that reduce the power loss in the PoE bridge at the end of the cable prior to delivering the power so when you reduce the loss of the diode bridge using a MOSFET and controller you can save thermals and reduce heatsinking. But for that you need PoE++.”

But customers also want the cells to be backwards compatible with all the specifications to power devices using 13W, 25W, 71W or 150W for the different PoE specifications and this is driving the adoption of the latest PoE++ specification to ensure that all kinds of cells can be powered by the infrastructure.

This is not just driven by the move to 5G, but an


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