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Description
The MAX5974A evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board featuring the MAX5974A active-clamped, spread-spectrum, current-mode PWM controller for Power-over-Ethernet (PoE) powered device (PD) applications. The EV kit is a compact and low-cost design used in Power-over-LAN (PoLAN) applications requiring DC power from an Ethernet network port for PDs such as IP phones, wireless access nodes, and security cameras.
The EV kit features a galvanically isolated 25W, 600kHz switching frequency forward DC-DC converter using the IC. The circuit achieves high efficiency up to 92% (VIN = +42V) using a coupled-inductor forward DC-DC converter topology. The surface-mount transformer provides up to +1650V galvanic isolation for the output. The EV kit output voltage is configured for +5V and provides up to 4.7A load current.
The EV kit includes the MAX5969B IEEE® 802.3af/at-compliant network PD interface-controller IC, which provides PD detection signature, PD classification signature, in-rush current control, and undervoltage lockout (UVLO).
The EV kit circuit receives its power from IEEE 802.3af/at-compliant power-sourcing equipment (PSE). The PSE provides the required -30V to -57V DC power over an unshielded twisted-pair Ethernet network cable to the EV kit's RJ45 MagJack®. The EV kit features a 1 x 1Gb RJ45 MagJack and two full-bridge diodes for separating the DC power provided by an endspan or midspan Ethernet system.
The EV kit circuit can also be powered by a +37V to +57V wall-adapter power source applied at the PWR+ and PWR- PCB pads. When a wall-adapter power source is detected, it takes precedence over the PSE source, allowing the wall adapter to power the EV kit.
Warning: The EV kit is designed to operate with high voltages. Dangerous voltages are present on this EV kit and on equipment connected to it. Users who power up this EV kit or power the sources connected to it must be careful to follow safety procedures appropriately to work with high-voltage electrical equipment.
Under severe fault or failure conditions, this EV kit may dissipate large amounts of power that 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.
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