"PoE controller" is a term that can encompass ICs that manage a PoE interface by controlling power delivery between a power source (or PSE, power source equipment) and powered devices (PDs). They accomplish this via current limiting, auto-classification, and detection. The new NCP1095 and NCP1096 interface controllers incorporate all of these features.
These devices take full advantage of the new IEEE 802.3bt standard, allowing up to 90 watts of power to be transferred over Local Area Network (LAN) connections. This is a significant improvement over the 30 watts provided for under IEEE 802.at.
The ON Semiconductor NCP1095 and NCP1096. Image from ON Semiconductor
ON Semiconductor complements the NCP1095 and NCP1096 with the NCP1566 DC-DC controller, the FDMC8622 single MOSFET, and the FDMQ8203 and FDMQ8205A GreenBridge Quad MOSFETs. These devices have been developed to provide a more efficient alternative to a diode bridge in PoE applications.
Taken together, these units enable PoE interfaces can go beyond the IEEE 802.3bt standard limit of 90 watts to a proprietary 100-watt solution if the extra power is needed. This advantage can prove to be useful for designers of telecommunications and digital signage systems.
The NCP1096 incorporates an internal n-channel MOSFET load switch, while the NCP1095 does not and requires an external pass transistor. These differences are noted on the lower left of the two diagrams presented below.
Block diagrams for the NCP1095 and NCP1096. Image from ON Semiconductor. Click to enlarge
Implications of the New IEE 802.3bt Standard
The new IEEE 802.3bt standard for PoE will serve to enable the provisioning of both power and connectivity to new network endpoint applications. The new 90-watt limit can serve to obviate the need for remote power sources that that would otherwise require a dedicated and typically off-line power source.
The result will be the elimination of the need for separate power cables. It will also serve to simplify network topologies and provide a more robust ‘plug and play’ user experience. These improvements have the potential to transform every vertical market touched by the IoT, by enabling more sophisticated endpoints operating across larger networks.
The IEEE 802.3bt standard also optimizes energy management through the new “Autoclass” feature. This innovation can enable powered devices to communicate their specific power needs to the power sourcing equipment. The result is that PSEs will be able to allocate exactly the right amount of power to each PD, maximizing efficiency.
According to Ryan Cameron, Vice President of Industrial and Off-Line Power Solutions at ON Semiconductor, “As a company focused on energy efficiency, we are really excited to help PoE achieve its full potential.” Cameron goes on to state that, “By providing a complete family of IEEE 802.3bt compliant solutions, we have made the technology more accessible for all development engineers which will help enable many more connected devices with guaranteed interoperability.”
Getting to Market Faster
To help designers get up and running more quickly, ON Semiconductors has made evaluation boards available for both of its new interface controllers:
Both evaluation boards incorporate the required functions of a PoE system such as detection, classification, and current limiting. They include RJ-45 connectors, a power transformer, active bridge, and other useful fixtures.
Around the Market
IEEE's 802.3bt standard is an important step forward, and many manufacturers are building products to take advantage of it.
- Maxim Integrated’s MAX5995B provide a complete interface for a powered device (PD) to comply with the IEEE 802.3bt standard in a Power-over-Ethernet (PoE) system.
- STMicroelectronics’ PM8805 includes two active bridges and their driving circuitry, a charge pump to drive the high-side MOSFETs, the hot swap MOSFET, and the interface compliant with IEEE 802.3bt.
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