MAX5941B

• IEEE 802.3af-Compliant PD Interface Circuit
• PD Detection and Configurable Classification Signatures
• Programmable Inrush Current Limit
• Programmable UVLO
• Isolated 13.2W Forward DC-DC Converter
• -36V to -60V Input Range
• Isolated +3.3V Output at 4A
• Receives Power from Endspan and Midspan Ethernet Systems
• -48V Power Interface for an External DC-DC Converter
• Local Power Inputs (Wall Cube)
• Fully Assembled and Tested

The MAX5941B evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board featuring an Ethernet port, network powered device (PD) interface and DC-DC PWM controller circuit for -48V systems. The MAX5941B is used in power-over-LAN applications requiring a DC-DC, fixed-frequency, isolated power supply from an Ethernet network port for PDs such as IP phones, wireless access nodes, and security cameras.

The MAX5941B EV kit receives power from IEEE® 802.3af-compliant power sourcing equipment (PSE). Refer to the MAX5922 and MAX5935 data sheets for PSE controllers. The PSE provides the required -44V to -57V DC power over an unshielded, twisted-pair Ethernet network cable to the EV kit. The EV kit features a 10/100BASE-TX voice-over-IP (VoIP) magnetic module and separate diode bridges for separating the DC power from the module provided by an endspan/endpoint or midspan Ethernet system.

The MAX5941B EV kit demonstrates the PD interface and DC-DC PWM features. The EV kit also demonstrates the full functionality of the MAX5941B. Features such as PD detection signature, configurable PD classification signature, programmable inrush current, and programmable undervoltage lockout (UVLO) can be evaluated. All of these features are configurable on the EV kit.

The MAX5941B EV kit also features a galvanically isolated, 13.2W, 275kHz switching frequency DC-DC converter, which uses the MAX5941B current-mode PWM controller section of the IC. Power for the forward DC-DC converter circuit is provided from the MAX5941B's -48V output, or from a local input DC supply, such as a wall cube. The DC-DC converter is configured for an output voltage of +3.3V and provides up to 4A. High efficiency (up to 85%) is achieved using a single transistor, forward DC-DC converter topology on the primary side, and synchronous rectifiers on the secondary side. The surface-mount transformer provides up to 1500V_RMS galvanic isolation for the output. UVLO, soft-start, and current limit provide a robust 13.2W isolated power supply.

Warning: The MAX5941B EV kit is designed to operate with high voltages. Dangerous voltages are present in this EV kit and in equipment connected to it. Users who power up this EV kit, or power the sources connected to it, must follow safety procedures appropriate for working with high-voltage electrical equipment.

Under severe fault or failure conditions, this EV kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of component debris at high velocity. Operate this kit with care to avoid possible personal injury.

Applications

• Computer Telephony
• Internet Appliances
• IP Phones
• Power Devices in Power-Over-Ethernet/Power-Over-MDI
• Security Cameras
• Wireless Access Nodes