MAX5991AETP+T

Power Over Ethernet (PoE) Controllers – MAX5991AETP+T Application Field and Working Principle

Power over Ethernet (PoE) is an industry standard defined by the IEEE 802.3af which simplifies the acquisition and deployment of network devices, by delivering both data and power through a single Ethernet cable. PoE technology is typically used to power devices such as VoIP phones, IP cameras and access points. The MAX5991AETP+T is a 15W, single/dual/quad Power Over Ethernet (PoE) controller IC optimized for enabling 15W PoE application over one to four twisted pairs of RJ-45 cables.

The MAX5991AETP+T features a wide input voltage range (6V to 54V) that can be used in both midspan and endpoint application. The MAX5991AETP+T is available in two versions: the MAX5991AETP and the MAX5991AETP+T. The MAX5991AETP+T is a version that contains additional diagnostic monitoring and protection circuitry such as short-circuit protection, thermal shutdown and over-current sensing. This version is ideal for 10/100/1000 Mbps, IEEE 802.3af-compliant system designs.

Applications of MAX5991AETP+T

The MAX5991AETP+T is ideal for 10/100/1000 Mbps, IEEE 802.3af-compliant, single/dual/quad, Power Over Ethernet (PoE) applications. Some of the applications where the MAX5991AETP+T can be used include:

• Security cameras/Video Surveillance
• Wireless Access Points
• Voice over IP (VoIP) phones
• Medical Applications
• Professional Audio Equipment
• Building Automation Systems
• Industrial Automation Systems
• Robotic and Automotive Controllers
• Factory Automation Systems

Working Principle of MAX5991AETP+T

The MAX5991AETP+T operates over a wide input voltage range of 6V to 54V. Internally, the device regulates the input voltage to an output voltage of 28V while providing up to 15W of power. The device also features three current sensing thresholds to allow it to automatically detect either 15.4W, 12.95W, or 4.5W of power draw from the endpoint. The device also contains integrated over temperature protection and short-circuit protection to ensure the safety of the system.

The MAX5991AETP+T provides accurate classification of the load type through its DC threshold detect pin. This allows the device to classify loads such as high power, midrange or low power. The device also contains built-in load disconnect circuit allowing for a dynamic load disconnect feature within short circuits for improved safety.

To protect the output voltage, the MAX5991AETP+T can be set up in an open loop or closed loop design. In an open loop design, the device features an adjustable over voltage protection circuit which trips the output voltage to a safe level when the output exceeds the user-defined voltage limit. In a closed loop design, the MAX5991AETP+T employs current limiting to ensure that the output voltage remains within safe limits.

Conclusion

The MAX5991AETP+T is an ideal choice for single/dual/quad Power Over Ethernet (PoE) applications such as security cameras/video surveillance, wireless access points, VoIP phones and medical applications. The device is optimized for 10/100/1000 Mbps PoE applications, with an input voltage range of 6V to 54V and an output voltage of 28V. It also provides integrated over temperature protection, short-circuit protection, and load disconnect feature for improved safety. Additionally, the device can also be set up in an open loop or closed loop design for output voltage protection.