Jul 24, 2016 | By: and

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The Power over Ethernet (PoE) trend is for higher and higher power ratings as new PoE-based IoT devices – security cameras, wireless access points, IP phones, micro base stations and even LED lights – require more to support new features and functionality.

However, increasing power ratings to 25.5W and higher isn’t the only goal keeping PoE device designers busy. Their other key design goals typically include:

  • Decrease product size
  • Minimize power losses to meet IEEE 802.3at standards
  • Keep costs down
  • Reduce heat generation

Excessive heat is a major concern for product designers since higher power ratings lead to increased temperatures in the Schottky diodes typically used in PoE devices.

The latest high definition (HD) security cameras are a great example of the need for more power and just how detrimental the heat generated by higher power ratings can be. These cameras are increasingly packed with higher performance processors; motors that can pan, tilt and zoom to follow the action; lights for night time operation and even heaters for cold weather operation.

While delivering sufficient power to operate these security cameras is straightforward, the heat generated by the diodes can degrade the video quality, which is unacceptable since HD’s superior resolution is the main selling point.

Designers have long used heat sinks and increased PCB size to physically distance hot diodes from heat-sensitive components to prevent devices from reaching temperatures that impact their operation. However, these are no longer ideal approaches as they make it harder to achieve the other PoE design goals.

For instance, adding heat sinks and using a larger PCB only increases the BOM and does nothing to cut costs. Additionally, trying to shrink a product design isn’t any easier with a large PCB. And, of course, using heat sinks and a larger PCB results in an inherently more complex design.


At Fairchild, we think a better way to counter excessive heat is to avoid generating it in the first place. This is the approach we’ve taken with the next generation of our GreenBridge™ technology. This new series of quad MOSFET multi-chip modules has ideal characteristics for PoE devices, including:

  • It dissipates up to 10x less energy than Schottky diodes
    • Far less heat generated eliminates need for heat sinks
    • PCB shrinks because it doesn’t have to be distanced from heat-sensitive components
  • It comes in a thermally-enhanced package
    • Keeps temperatures down
  • Best-in-class RDS(on) maximizes power for PoE devices
    • Low losses result in superior efficiency
  • Small 4.5 mm x 5 mm MLP package
    • Smaller package means smaller PCB
  • It doesn’t require any external drivers
    • PCB can be shrunk even further
    • Simple and clean circuit layout
  • It supports increased power without impacting 802.3at compliance
    • Standards compliance is a strong selling point for many PoE devices
  • It is expected to support the future 802.3bt standard for >50W
    • Standards compliance will likely be more important in the future

It’s clear that the trend of PoE-based IoT devices requiring higher power ratings will only accelerate as manufacturers continue adding more features and functionality to compete and maintain their profit margins.

It’s also clear that the Schottky diodes that have been acceptable solutions have become a burden as adding heat sinks and using larger PCBs to counter the heat they generate at higher power ratings makes it harder to achieve BOM and size goals.

We have worked closely with our POE customers over the years and thanks to their input, have seen these demands coming. We prepared by developing our next-generation GreenBridge technology as a true solution to enable them to meet their innovation goals while also meeting their business requirements. Are you seeing the same pressures for your PoE roadmap development, as well?

Visit the  product folder to download the datasheet, order samples, and read the app note.

For more technology information, visit the GreenBridge landing page.


This post is also available in: Chinese (Simplified)