1 Application Brief

Power over Ethernet (PoE) solutions offer flexibility to users. System design may be configured to support different features, optimize size and BOM, or offer more control. Texas Instruments (TI) offers various resources, in the form of Evaluation Modules (EVM), Training Videos, and User Guides that can be leveraged for individualized system design. Three different Power Sourcing Equipment (PSE) system software solutions are outlined in this brief.

FirmPSE

The first solution utilizes TI’s system-level firmware solution, FirmPSE. FirmPSE is used to evaluate and create production-ready PSE system firmware code. FirmPSE is popular for multi-port applications as its power supply management features help optimize use of multiple and lower-power power supplies. Port power management (PPM) features can configure a system to power a PoE Powered Device (PD) only if there is enough remaining power and allocate priority (low or high) to ports for structured shutdowns. FirmPSE reduces time to market and saves software resources by excusing users from having to write the code to control PSEs.

No Host Controller: Autonomous Mode

TI’s TPS23861 device, a four-port PSE solution, and TPS23882, an eight-port PSE solution, support Autonomous Mode. This operating mode is in addition to the existing auto, semi-auto, and manual modes. A significant benefit of autonomous mode is that it does not require host or I²C communication, meaning no software is needed. At a BOM and PCB level this means there can be an absence of the MSP430 daughter card and all signal-related communication components. Furthermore, the FirmPSE GUI is not needed as there is no software to debug. The TPS23882B device is an IEEE802.3bt two-pair compliant solution and the resistance on the AUTO pin determines either Type 3, Class 4, 30 W per port or Type 3, Class 3, 15.4 W per port. The TPS23861 device only offers 30 W in Autonomous Mode.

This system solution is preferable for lower port counts where PPM features are not required. Power supplies should be able to support full power at all ports. Additionally, predetermined per port power makes autonomous mode an ideal application for PoE midspan injectors. Table 1-2 references TI's resources to facilitate autonomous mode.

User-Defined MCU

In the case that the MSP430 MCU will be replaced, users can create their own system software. To start development, leverage the MSP430 reference code in Table 1-3. This system solution is best suited for users that desire more flexibility and configuration control. The following resources also consist of user guides detailing registers in the PSE chips. Register hex values can be used to design the microcontroller. The EVMs can be used to benchmark code.

Conclusion

In conclusion, each system design offers different levels of control and functionality. Texas Instruments offers multiple resources to promote solution flexibility. In addition to the previously-mentioned resources, TI’s training videos and E2E? Forum can help with creating an individual system solution.