IEEE 802.3at PoE Powered Device (PD) EV Board
EV3908+8002-00A is designed as the Power over Ethernet (PoE) Powered Device (PD) module. An RJ-45 connector is provided to connect directly to an Ethernet cable having a Power Sourcing Equipment (PSE) driving it on the other end. It also accepts power applied using a stand-alone power supply.
According to the IEEE 802.3at specification, the PD module must provide the circuitry needed to be detected by the PSE as it polls the Ethernet links. The IEEE 802.3at specification also allows the option for the PD to provide classification as to the amount of power needed by the PD Module. EV3908+8002-00A with the MP8002DN provides all the necessary hardware to provide detection and classification together with programmable inrush current limit, power good indicator, thermal protection and current limit. An external 30W Flyback converter is connected as the PWM part of the PD, which is controller by the synchronous PWM controller MP3908DS with soft-start, slope compensation and peak current limiting.
- Meets IEEE 802.3at Specifications
- 100V, 0.8Ω Integrate DMOS Device in MP8002DN
- 450mA, Temperature Compensated Current Limit
- Open Drain Power Good Output
- Synchronous Rectification for MP3908
- Current Mode Control
- 250kHz Constant Frequency Operation
Current Mode PWM Controller with Synchronous Gate Drive
The MP3908 is a flexible current-mode PWM controller optimized for power-supply applications. The MP3908 features resistor-programmable dead-time control to optimize efficiency for a broad number of different configurations, and a synchronous secondary gate drive. The MOSFET drivers are capable of driving >10A MOSFETs. It has an operational current of typically 270µA and can accommodate off-line, Telecom and non-isolated applications. Under-voltage lockout, soft start, slope compensation and peak current limiting are all included. In a boost application, with an output voltage of less than 28V, the current sense pin can connect directly to the drain of the external switch. This eliminates the requirement for an additional current sensing element and its associated efficiency loss. While designed for boost applications, the MP3908 can also be used for other topologies including Forward, Flyback and Sepic. The 10V gate driver compliance minimizes the power loss of the external MOSFET while allowing the use of a wide variety of standard threshold devices. An externally programmable delay following the turn off of the synchronous rectifier allows the incorporation of secondary side synchronous rectifier. The MP3908 is available in space saving 10-pin MSOP package.